DBMS SQL DAY 12

DAY 12

1.      DML: Data Manipulation Language

DML commands are not auto-committed. It means changes are not permanent to database, they can be rolled back.

Command	Description
1. Insert	to insert a new row
2. Update	to update existing row
3. Delete	to delete a row
4. Merge	merging two rows or two tables
Data Manipulation Language (DML) statements are used for managing data in database. DML commands are not auto-committed. It means changes made by DML command are not permanent to database, it can be rolled back. 1)      INSERT command Insert command is used to insert data into a table. Following is its general syntax, INSERT into table-name values(data1,data2,..) Let’s see an example, Consider a table Student with following fields. S_id S_Name age INSERT into Student values(101,'Adam',15); The above command will insert a record into Student table.  S_id S_Name age 101 Adam 15 Example to Insert NULL value to a column Both the statements below will insert NULL value into age column of the Student table. INSERT into Student(id,name) values(102,'Alex'); Or, INSERT into Student values(102,'Alex',null); The above command will insert only two column value other column is set to null. S_id S_Name age 101 Adam 15 102 Alex 2)       UPDATE command Update command is used to update a row of a table. Following is its general syntax, UPDATE table-name set column-name = value where condition; Lets see an example, update Student set age=18 where s_id=102; S_id S_Name age 101 Adam 15 102 Alex 18 103 chris 14 Example to Update multiple columns UPDATE Student set s_name='Abhi',age=17 where s_id=103; The above command will update two columns of a record. S_id S_Name age 101 Adam 15 102 Alex 18 103 Abhi 17 3)       Delete command Delete command is used to delete data from a table. Delete command can also be used with condition to delete a particular row. Following is its general syntax, DELETE from table-name; Example to Delete all Records from a Table DELETE from Student; The above command will delete all the records from Student table. Example to Delete a particular Record from a Table Consider the following Student table S_id S_Name age 101 Adam 15 102 Alex 18 103 Abhi 17 DELETE from Student where s_id=103; The above command will delete the record where s_id is 103 from Student table. S_id S_Name age 101 Adam 15 102 Alex 18