SQL Course For Beginners 2024

1. Introduction to SQL Course: Welcome to the beginner course of complete Cule. In each class, we are going to discuss the SQL from basics to advance. In basics, we are going to discuss about how to create the table, how to display the table values, and how to insert the values. In the advance, we are going to discuss about the inner joins, outer join and other joint conditions. And also we are going to discuss the group bi conditions, order bi conditions, and other conditions we are going to discuss in the advance Cule. So this course is very, very, very useful for the students who are studying SQUL for the first time. For that only, I'm discussed the basics of SQUL to the advance of the SQUL. So let's see the course 2. Sql Class 1 : History Of Sql: First class. In today's class, we are going to discuss about the complete introduction of the SQL. SQL stands for the structured quarri language. So this language is very used for the data retrieval from the database. You can also use SQL to manipulate and change the data in the database. And the second one we are going to discuss is about the importance of SQL there are three important of SQL. The first one is the efficient data retrieval, and the second one is the data security and the third one is the scalability. The first we are going to discuss is the data retrieval. SQL enables quick and efficient retrieval of data from the database. We can use the SQL to retrieve the data very fast from the database. And the second one is the security. Database security is very, very, very important. So that's the importance of the SQL. So SQL ensos the database is more secured one. And the third one is the scalability. The scalability is nothing, but we are going to provide the resources based on the consumption of the consumers. That is the users. If the users want more data, we are going to provide them more data for that user. If that user wants lower amount of data, we are going to provide lower amount of data for that user. That is the scalability. And the third we are going to discuss is about the DDL DML and DCL commands in the SQL. So the DDL stands for data definition language. There are three commands in the DDL. The first one is the create and the second one is the alter, and the third one is the drop. And the second is the DML command. DML stands for data manipulation language. So there are many commands in the DML. The first one is the insert and the second one is the update, and the third one is the dilate. And the third one is the DCL, DCL stands for data control language. There are two commands in the DCL. The first one is the grant and the second one is the revoke. And the fourth topic we are going to discuss is about advantages of the SQL. And the first one is the data integrity. So there are many constraint and rules for the SQL to provide data integrity. Data integrity is nothing, but there will be no changes in the data which is stored in the database. And the second one is the transaxen control. So there are many transaxen controls like acid property, the acid strands for the A strands for the atomty and the C stands for consistency, and the I stands for isolation and the D stands for durability. So these are all the transaxon control. And the third advantage is that data independence. There will be no data depending on other data to perform their axons. And the last topic we are going to discuss is about the SQL job opportunities. If you study SQL from the basics to advance, you can have these job opportunities. The first one is the database administrator, and the second one is the database analyst, and the third one is the database developer. So if you master the SQL, you can have these job opportunities. So that's it. In today's class, we will discuss about the complete introduction of the database language, that is the SQL. That is structured query language. 3. Sql Class 2 : Create Table: And in today's class, we are going to discuss about how to create our table in the cle squal. For that, you have to type the syntax for the creation of table in the Aclsqud. For the first, you have to type the create table. Name table name can be your own choice for that our table name is students. After typing the table name, you have to type the open brackets. Inside the open brackets, you have to type the row heading values. For our table students, they have their own name, age, department, and course. These are the row heading values. For that, we are going to type these row heading values inside our table. For the first, we are going to type the role number of the students. The role number must be an integer data type. Also the role number is init for each students. For that, I'm choosing the role number as primary key. These primary key and faring key can be explained in the upcoming classes. After typing the role number, we are going to type the name of the students. For that, the name of the students must be an data type. It must not be an integer data type. Inside the bracket of the WCA, you can type any number of values. After typing the name of the students, we are going to type the row heating value for the course. Course must be also a CAR data type. Inside the brackets, you can type any number of values up to 255. And then we are going to type the department of the students. So department is also a CAR data type. At last, we are going to type the age of the students. The age of the students must be an integer data type. So age is integer data type. After typing all the row heading values, you have to put close bracket and class with the semicolon. So this is the syntax for the creation of table in the racLEcL. You can see in the first row of our student table, the role number is the primary key. These primary key and far in key can be explained in the upcoming classes. In the second one, there are many data types. The first one is the WCR datatype and the second one is the integer data type, and the third one is the Boolean data type, and the fourth one is the float data type, and the fifth one is the binary datatype. So there are many other datatypes in the SQL. The most, we are going to use the VCR data type. After that, we are going to run this SQL command. For that, you have to select all the commands, and then you have to select the run SQL statement. So you can see our table is created in the SQL developer. So this is the format of creating the output in the SQuL developer. After that, we are going to create the second table, the teacher's table. The first table is the student table, and the second table is the teacher table. For the same syntax for the creation of the table. You have to type the create table, and then the table name. The table name can be your own choice for that our table name is teacher. And then you have to type the open brackets. Inside the open brackets, you have to type the row heading values. For the first, we are going to type the ID of the teachers. The ID must be an integer data type. So it also unit you for each teachers. For that only, it is a primary key. And then we are going to type the name of the teachers. The name must be VCR data type. So inside the brackets, you can type any number of values up to 255. And then we are going to type the course that also the R data type, and the department, it also the WAR data type. At last, the age of the teachers, the age must be an integer data type. After typing all the row heating values, you have to close the bracket and put semicolon at the end. After typing these commands, you have to run this SQUL command. For that, you have to select all the commands and select run SQL statement. So you can see the second table is created, the teacher table is created. So this is the format for creation of table in the Oracle escule. So that's it. In today's class, we discussed about how to create the tables in the Oracle escule. In the upcoming class, we are going to discuss about how to insert the values in the created tables. 4. Sql Class 3 : Insert Values: Last class we discussed about how to create the table in the RCL scull. In today's class, we are going to discuss about how to insert the values in the created table. In the last class, we have created the two tables, the student table and the teacher's table. We are going to insert the values in the each tables we have created. First, you have to type the insert, and then you have to type into Inset into. After that, you have to type your table name. After that, you have to type your table name, and then you have to type the values inset into table values. So this is the syntax. And then you have to type the open bracket. In that, you have to type the values for the tables. The first one is the roll number and the second one is the name, and the third one is the course, and the fourth one is the department, and the fifth one is the age. So you have to tie these values inside the brackets. First, we are going to type the roll number that is 100 and the second, we are going to type the name, and then you have to type the course name. That is mass. And then you have to tie the department name. So department can be your own choice, whether it is CSE or EC or E or IT or mechanics. And the last one is the He, so age of the students. And then you have to close the bracket and put semicolon at the end. So this is the syntax for creation of the values inset. So you have to tie inset into students. The students is the stable name. And the values inside the brackets, you have to type the values of the tables. The first one is the roll number and the second one is the name, and the third one is the course, and the fourth one is the department, and the fifth one is the age. After that, we are going to run this SQUL command for the insert of values in our tables. For that, you have to select this line only. So we have successfully inserted our values in the created table. After that, we are going to insert the values for the five times. For that, you have to copy this line and paste it as five times. After that, you have to change the values for each columns. For the first, we are going to change the role number and the second, we are going to change the name, and the third, we are going to change the department, and the fourth, we are going to change the course, and the last, we are going to change the age of the students. So you have to change them for your own choice. You can type any number of values or any number of names, coures or department for your table. Changing the values, you have to run this command again for the insertion of values in our tables. For that, you have to select all the commands and select run SQL command. So you can see there are four rows are created for our table students. So we have to insert the values for the second table that is teacher. For that, you have to type the same command insert into the table name that is the teacher. After that, you have to type the values, and then you have to type the open brackets. Inside the open brackets, you have to type the column values. For the first, that is ID and the second one is the name, and the third one is the course and the fourth one is the department, and the fifth one is the H. You have to type one by one. After typing these values, again, we are going to insert these values for the five times, for that you have to copy this command and paste it as five times. And then you have to rename the values. After changing the values, you have to run this command. For that, you have to select these commands only. So you can see there are five rows are created for our table teachers. So that's in today's class, we discussed about how to insert our values in the created tables. For that we are creating the two tables, the students table and the teacher's table. 5. Sql Class 4 : Select Command: Welcome, everyone. In today's class, we are going to discuss about the salt condition. So Salet is very, very useful for displaying all the values created in the table. For that, we are going to use the Salt command in our class. So let's get started. For that, we have to type the salt star represents, it display all the values created in the table. F which table you have to type the table name, that is the students. So at last, you have to select the semicolon. So this is the first type the star represent, I displays all the values created in the table. After typing that, you have to select this command and select run SQuL statement. So you can see all the values created in the table students are displayed in our STUL developer. The first one is the roll number and the second one is the course, and the third one is the department, and the fourth one is the age. So you can also see the values for each rows and columns. So in the previous class, we are insert the values in the tables. So these values are sewn using the SeLT command. After that, we are going to discuss the two commands with the select. The first one is the distinct. The distinct removes the duplicate values from the table. It sews only the one time of the value and removes the repeton of the same value. For that Oto tights select distinct so your column name, whether it is department name, age, or ID or course, from the table name. The table must be students or teachers. So it removes the duplicate values from the course. If the course contains two or more same values, it removes them. You have to select this command and run this command. After that, you can see the distinct course value from our students table. So in the students table, you can see the mass is repetated or duplicated. For that, the distinct removes the mass value from our course. It shows only the one time of that mass. After that, we are going to discuss the second one that is the unique values. So unique is same as the distinct value. It also removes the duplicate values from our table. Unique, so unique is the keyword. You have to type your course or department name or any other column name, and then you have to type the from with the table name. So it removes the duplicate values from our table. So it also same as a distinct one. So we are going to select the unique department from our teacher table. So in the teacher table values, you can see the CSE is repetated. For that, the unique removes them and source only the one time. 6. Sql Class 5 : AND OR NOT Command: Hello, everyone. In today's class, we are going to discuss about the and or not conditions. For that, you have to type this syntax, select name course from the table name, that is the students were condition, and then you have to type the age or any other conditions, age greater than 20. And roll number must be equal to 100. So these two condition must be satisfied for the displaying the values of names and codes from the student table. So is based on both condition must be satisfied. If the age equal to 20 and the role number equal to 100, so these two conditions must be satisfied. After that, only these values are displayed. So if any one of the condition is not satisfied, so the is not displaying the values. So after that, you have to run this command. So you can see the output value which is satisfy the condition. So in our students table, the age and role number must be satisfied. The role number must be 100 and the age must be 20. For that, these two conditions are satisfied. So we are going to display the name and the course. For that, you can see the name and the course of the table. So this is the use of the conditions. Both conditions must be satisfied. So R condition is based on if any one of them is satisfied, it displays the values. And is based on both conditions must be satisfied. R is based on if any one of them is satisfied, you can display the values. If the A equal to 20 or roll number equal to 100, if any one of them satisfied, it source the values. So you have to run this command. After that, you can see the values displayed in the 12 developer. So you can see the first row, the age is 20. For that, you can see the name and the course. You can also see the roll number is 100. Both conditions are satisfied. You can also see the name and cos are displayed. In the second one, you can see the age is 20. The one condition is satisfied. For that, you can see the in row is displayed. After that, we are going to display the third command that is not condition. So not is based on displaying the values except the naught condition. For that, you auto type, select, name, course from student table where condition, not Age equal to 20. We are going to display the name and course from the student table, which the H must not be equal to 20. So that is the definition of the nut. The nut source, it must not be displayed. If the H equal to 20, these name and course must not be displayed. So it removes the not conditions and sows the other values. After that, you can see the name and course displayed for our knot conditions. So if the age equal to 20, these rows must not be displayed for our table. So that's it. In today's class, we are discussed about the three commands. That is the first one is the and and the second one is the R and the third one is the 7. Sql Class 6 : Min & Max Command : Come, everyone. In today's class, we are going to discuss about the two conditions, that is min and max conditions. In the previous class, we discussed about the or not condition. For the min and max, it source the minimum value and the maximum value in our table. For that only, the min and max are used. For that, you have to type this command for the min and max conditions. The first one is the select. We are going to display the values. And then you have to tie the men of the row or column name. For that, we are going to select a minimum age from our table. That is the students. So it sorts the minimum age values in our table students. After that, you have to run this command, so you can see the minimum age value in our table students is 20. So in our inserted values, the 20 is the minimum value. For that only it sows the minimum age that is 20. So other values are greater than 20. After that, we are going to discuss the maximum condition. Select max of age from student. So it shows the maximum age value in the student table. So you have to run this command. So you can see the 25 is the maximum value in the student table. Today's class, we are discussed about the min and max conditions. The min max and conditions are very useful for if you want to display the minimum values or maximum values from the table, you can use that min and max conditions. 8. Sql Class 7 : Alias Command: Hi, everyone. In today's class, we are going to discuss about the As condition. As Cdison is very, very useful for. If you want to change your own name as your own convenient, you have to use the AS condition. For that only, the AS condition is very useful. We are going to type the select command, and then we are going to use the aggregate function that is min of H. And then you have to tie the AST word. And then you have to tie the convenient name for the mean of H. So we are going to tie the minimum H. So the sky word changes the men of g name to minimum H for our own convenience. And then you have to type the from condition with the table. And then you have to type the table name from table name. So the a changes the min of g to the minimum age. After that, you have to run the command. So you can see in the output it sows minimum age. So the aS keyword changes the name min of g to the minimum age. So the minimum age is 20 in our student table. So if you remove the ASK word and then run the command, so you can see the men of H. So it goes through the default name of the SQL developer. So that's it. In today's class we discuss about the Akword. So ASK word is very, very useful for reining the default one to the convenient name of your own choice. 9. Sql Class 8 : Like Command : One. In today's class, we are going to discuss about the condition. In previous class, we discussed about the order by having the group by condition. We are going to display on one example for that, you have to type, select name from students with the ware condition where the name must be, so you have to time the name. So whether the name start at Run it must be displayed in our SQL statement. If the values in our table starts with the name Run, it must be displayed in our STL output. For that only, you can use the lie condition. If the name starts like As, B, or any other RN g or any other Kumar, or any other one, you can use the lie condition. After that, you have to run this command. So you can see there are only one name starts with a Run. So you can see there are only one value which starts with the Run. So we are going to see the other example. So we are going to display the names started from the Bala. If the name started with Bala, it must be displayed. In that, you can see there are no names started with Bala. So in our table, you can see the name started with Bar Siva. There is no name started with Bala. For that only, you can see the output display no name started with Bala. If I type Bara Siva, it shows the output. Let's so you can see the name started with Barlaseva. After that, we are going to display the wildcard conditions. For the wild card, you have to type the percentage. If the name starts with the A, it must be displayed. For that only the percentage is used in the wild card. So you how to type A percentage. A percentage means A started in the table. So you have to type A percentage. It shows that whether the name started with the A, it must be displayed. You can see in the output, there are two names which are started with the alphabet A. If the percentage comes before the alphabet, it shows that names ending with the alphabet must be displayed. So there are two wild cards with the percentage. If the alphabet comes before the person dates, it shows the starting. If the alphabet comes after the person dates, it shows the ending. So we are going to display the names which are ending with the alphabet, so there is only one name which ended with the alphabet A. You can also see the other example. We are going to display the name which are ending with the alphabet. So there is only one name which are ended with the alphabet N. After that, we are going to discuss the naught like condition. For that, we are going to discuss one example in that we are going to display the name from the student table, which the name must not be it Run. Except Run we are going to display all the names. For that only, you can use then condition. So you can see, except the RN, all the names are displayed. So that's it. In today's class, we are discussed the two condition. The first one is the light condition, and the second one is the not light condition. In light condition, we are discussed the 21, the percentage coming to the front and the percentage coming to the last. 10. Sql Class 9 : Count Avg Sum: One. In today's class, we are going to discuss about the aggregate functions. So there are many other aggregate functions in the SQL. The first one is the min and max, we are discussed in the previous class, and the second one is the count, and the third one is the average and the fourth one is the sum. The first, we are going to discuss the count. For that, you have to type select and then you have to type the count aggregate function. After that, you have to type the open bracket. Inside the open bracket. Inside the square bracket, you have to type the display values. For that, we are going to type the age. After that, you have to close the bracket and type from table name. So it source the count of H from our student table. The count is very, very useful for if you want to count number of values present in your table, you have to use the count aggregate function. For that, we are going to count number of ages present in our student table. So you can see the output five. It source number of counts for the age is five. In the student table, we have inserted five age values for our table. 20, 25, 24, 20, and 22. So there are five counts. For that only source five for our count of age. So you can also use and son with the aggregate functions. For that, you have to type, select count of age from the table name with the condition, the condition must be age greater than 20. So we are going to count the ages which are greater than 20. You have to run this command, so you can see there are three commands, so you can see the count is three. So there are three ages which are greater than 20. So you can see the 25 24 and 22, which are greater than the age 20. So the output source the count of three. After that, we are going to discuss about the second aggregate function that is average. Yeah. So how to type this form, select average of roll number. So we are going to select the average of roll number from the table name, that is the students So this is the format for the average. We are going to average the roll number from the student table. After that, you have to run the command. So you can see the average of the roll number is one n two. So you can see the middle value is one n two. So average shows the middle value. So in our student table, one n two is the middle average value. After that, we are going to discuss about the last aggregate function that is sum. So for that, you have to type this select sum of ID or any other roll number or any other one from the table name. So it sums all the IDs in the teacher table. Then you have to run this command So the output source the value thousand and ten. So you can see it sums all the ID values which are inserted in the teacher table. You can see the 200 plus 200 plus 200 plus 200 plus 200. It goes to the thousand So that's it. In today's class, we are discussed about a three aggregate function. The first to is the count and the second one is the average, and the third one is the sum. 11. Sql Class 10 : Order By Command: We are going to discuss about the order by condition. Order by condition is based on the two values. The first one is the descending order and the second one is the ascending order. So we are going to discuss one of the examples for that, you have to tie, select. So we are going to select the name from the student table. After that, you have to tie the order by keyword, and then we are going to order the names from the ages for this example source, we are going to select the name based on the edges. So that's the useful of the order by condition. We are going to order the names based on the edges. The default order by is the ascending der. For that, in our example, we are going to display the names based on the ascending edges. So you can see all the names are displayed from our students based on the order by of age in the ascending order. So in the student table, we insert the values of the ages like 20, 25, 24, 20 and 22. So these names are based on the order of the ages in the ascending order. After that, we are going to discuss the second value that is the descending order. For that, you have to type, select, name, frame, the student table. After that, you have to type the order by condition. We are going to order by ages with the descending values. So in displace the name based on the order of the ages with the descending values, that is large too small. So it is the opposite of the ascending order. So in the upcoming class, we are going to discuss about the group pipe condition. 12. Sql Class 11 : Group By Command: Welcome everyone. In today's class, we are going to discuss about the group by condition. So group by condition is used for the aggregate functions like min, max, count, average sum. For that only, you can use the group by conditions. For the group by condition, you have to type the syntax. For the first, we are going to use the select condition, and then you have to type the aggregate functions like min of H, count of H, max of H, any other aggregate functions, and then you have to type the student table name. After that, you have to type the group by condition keyword. So we are going to group the values of minimum age with the name. So you have to run this command, so you can see the minimum of age based on the group by name. So if the name contains the alphabetic order, it changes the age according to the name. So in the student table, the minimum age is 20. For that, you can see the first value that is 20 is presented in our output. So that's it in today's class, we discussed about the group Pi condition. So group B gradison is very useful for the aggregate functions. 13. Sql Class 12 : Having Command: Everyone. In today's class, we are going to discuss about the having condition. So having condition is alternate to the W class. So we class is not used for the aggregate functions. For that only, we are going to use the having conditions for the aggregate functions. So we are going to see an example one so you have to type the select name from the student's table. Having keyword, you have to type the aggregate functions, whether it is Min of H, max of H, count of H, sum of H, average of H. So we are going to type the Min of H with the condition greater than 20. So it is same as the ware class, but we are going to use the having condition for the aggregate functions. So we are going to select the name from the students which are having the minimum of age greater than 20. So you can also see in the previous class we have used the were condition. So W is also same as we age greater than 20, but it is not used for the aggregate functions. For that only we are going to use the having condition. Before running the having condition, you have to type the group by condition, which are discussed in the previous class. So we have to type the group by condition. After that, only you have to type the having condition. In the previous class, we are discussed the minimum of H greater than 20, which are grouped by the name of the alphabetic order. If the A comes first with the minimum H, it sows in the first value. The first one AJ Kumar, that is 25, the alphabet stars A. For that, it sows in the first place. And the second one is the Mnoch, the manoch having the wage of 22, which is greater than 20. For that, it sows in the second one, and the third one is the ba CVA. The balus age is 24, which is greater than the 22. So that's it in today's class we discuss about the having condition. Having is alternate to the war condition because it is used for aggregate functions. 14. Sql Class 13 : Union Command: Today's class, we are going to discuss about the union command. If you want to combine the two commands, you can use the union command. For that, we are going to discuss an example. For that, we are going to discuss an example with other two selet commands. If the statements are not equal or save, the union command source the error. So after typing the two statements, you have to run the command. So you can see the display sows the two commands of the select. The first command is the select star from the students. It displays all the values from the student. And the second is the select star from the teachers. So it displays all the values in the teacher table. So you can see the union is used for combining the two statements. 15. Sql Class 14 : Inner Join: Today's class, we're going to discuss about the joint conditions. So there are many joint conditions in SQL. But in our class, we are going to discuss about the four joint conditions. The first one is the inner join and the second one is the left join, and the third one is the right join, and the fourth one is the full join. For the inner join, we are going to create a two tables. We are going to match the common values between both tables. For that, only we can use the inner join. So we are going to select the first table that is the student table and the column value, that is course, you have to type student dot course. That is table name dot column. After that, we are going to select the second table that is teacher with the column name. That is course. After that, you have to type from the first table that is students. Then you have to type the inner join keyword and the second table name. And then you have to type the on condition. After typing the on keyword, you have to type the column, which are matches in the both table. For that only, you have to type after the on keyword. You have to type the common values between the tables. So this is the syntax for the inner join condition. First, we are going to select the two values from each table, that is the select student dot course teacher dot course. After that, you have to tie the two table names that is from students inner join teacher. And then you have to type the keyword. After that, you have to type the common value matches between both table. So in our example, the common value between both table are department. After that, you can see that there are two courses are created. That is student table course and the teacher table course, which are matches with the common values, that is student department and the teacher department. So in the values of the students and the teacher, you can see the signs and the mass. The first one is the signs and the second one is the mass. In the signs, you can see the CSE department this matches with the second table, mass with the CSE department. So these two department are matches with both. For that only, the sine course is matches with the mass course. So that's it. In today's class, we discussed about the inner join. So inner join matches the common values between the both table. So in the upcoming class, we are going to discuss about the left join and the right join. 16. Sql Class 15 : Left Join & Right Join: And in today's class, we are going to discuss about the two joints, that is the left join and the right join. In the previous class, we discussed about the inner join. So inner join matches the common values between the both tables. For the first, we are going to discuss the left join. In the left join, it matches the values which are common in the left table. For that, you have to type the selet command, and then you have to type the table name within the column name. That is the table name dot column name, and the second table name with the column name. From the student table, left join, the second table, that is the teacher table. The student table is the left table. Teacher table is the right table, and then you have to type on keyword. After that, you to type the common values between each table. That is the department is common between both tables. So we are going to display the common values which are present in the left table that is the student table. So that is the use of the left join. So you can see the output is displayed for the left gin. For the first, you can see the sins and the mass. In the sins, you can see the CSE department is common. In that student table with the teacher table, the mass with the CSE department. So there are two CSE department which are common. For that only it sows the sines and mass. So we can also see the second row that is the mass and the mass. In the mass, you can see the CAE is common in the student table. And the second table that is the teacher, it also contains the mass and the CSE. For that only left joins and source the display values. So after that, we are going to discuss about the right join. So in the right join, it matches the common values in the right table. That is the teacher table. The student table is the left table, and the teacher table is the right table. So it commonly matches the values which are present in the write table. So you have to change the left join to the right join. Other commands are the same as the left join. So you can see the output results, so is the mass and the computer. So you can see the mass contains the CSE matches with the computer CSE. So that's it. In today's class, we discussed about the two joins the left join and the right in. 17. Sql Class 16 : Primary key: However, in today's class, we are going to discuss about the primary key far in key, check constraint and not null constraint. So these are the constraints we are going to discuss in today's class. First, we are going to discuss about the primary key. So the primary key is unique for the table. So it does not contain any duplicate values or any other repetated values. It must be unique for that in the table of the student, the role number is unique for each student. For that only, the role number is the primary key of the table students. You can also see the name, course, department, engage. These can be duplicated or same for each students are same for two or more or students. The name can be same for two more students. For that only you cannot use the primary key for the name. So you have to use the primary key for the unique keyword. And the second, we are going to discuss about the far in key. Far in key is the reference of the primary key. For example, if we create two tables, the student table one and the student table two, in the student table one, the role number is the primary key. If you want to create the primary key in the second table also, we can use the far in key. The far in key reference as the primary key. So it also the same as the primary key. Third one we are going to discuss is about the check constraint. If you want to insert the values based on some conditions, you can use the check constraint. For that, in our table, we are going to use the check constraint for the age. If the age must be greater than 20, then only we are going to insert the values. If the age less than the 20, we are not going to insert the values. It is same as the were condition. But the ware condition is used in this select, but we are going to use the check constraint in the table also. So it checks the age greater than 20, then only it enters the values. If the age less than 20 is entered in that table, it shows the error. At last, we are going to discuss about the last constraint that is not null. So naught null is used for if we enter any null values, it shows the error because we have used the naught null constraint. So that the table must contains each row, each column values. It must not be an empty cell or empty null. So for that, only not null is used. 18. Sql Class 17 : Alter Command: As we are going to discuss about the alter table condition. In the alter table, there are two conditions are available. The first one is the add and the second one is the drop. We are going to discuss these two condition one by one. For the first, we are going to discuss about the add column condition. For that, you have to type the command alter table, table name. After that, you have to type the keyword add. If you want to add columns, extra columns for your table, you have to type this command. You have to type your column name, that is the new column name with the data type. For that, the gender must be CR data type. After typing that, you have to run this command. So you have to run this command so you can see the student table is altered. If you display the student table with the set command, you can see the new column is added. If you want to delete any columns, you have to type the drop column command. For that, you have to type alter table, the table name, and then you have to type the keyword drop column. And then you have to type the column name. For that, we are going to delete the column gender. Then you have to run the command so you can see the table is altered because the column is deleted. After running the select command, you can see the error is zoned because we are deleted the column gender or that only sows the error. So that's it. In today's class, we discussed the alter table command with two conditions, add column and then draft column condition. 19. Sql Class 18 : Drop Table: In today's class, we are going to discuss about the two conditions. The first one is the drop table condition and the second one is the truncate table condition. These two conditions is very, very important for the interview of SQL cotins. You have to remember which condition performs which axons. First, we are going to discuss about the truncate table. So Truncate is very useful for if you want to remove the values insert the table, you can use the truncate table. Truncate removes all the values inserted in our cable. For that, you have to type truncate table table name. So it removes all the values inserted in the table. So you have to run the command before running the command, we are going to display what are all the values inserted in our table. So you can see these are the values inserted in our table student. After that, we are going to truncate this table. That is removing all the values from this table. So you can see the student table is truncated. Again, we are going to display the student table. In that you can see all the values inserted in our student table are removed. So that is the use of the truncate table. It removes only the values. After that, we are going to display the drop table condition. So drop table is very useful for if you want completely remove the table, you can use the drop table condition. So that is the difference between the truncate and the drop. Truncate removes the values. Drop removes the complete table. If you run the Slet command of the student table, you can see the error is zoned because the error sows the table created because we deleted the table using the drop table condition. So that is the use of the drop table condition. So you must remember which command performs which axon, Trant performs remove values. Drop performs delete table.