Data Manipulation Language in SQL

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Introduction to Data Manipulation Language in SQL

Data manipulation language is used to retrieve information from the table and modify the data which is present in the table this language in SQL is widely used to retrieve data from multiple tables.

commands of DML in SQL. 

  • SELECT – retrieve data from the database
  • INSERT – insert data into a table
  • UPDATE – updates existing data within a table
  • DELETE – deletes all records from a table, the space for the records remain.

With the help of these commands of DML, we can retrieve, modify, insert the data from the table. 

Select Command

Select command in SQL is used to select the columns from the table to retrieve the rows from it.

Without a select clause, we cannot retrieve the rows from the table. 

Syntax of Select Command:-

Select [Column_name]

From [table name]

Cndition_Clause [Condition column];

For example:-

Display first_name and salary from the employees’ table?

Query:-
Select first_name,salary 
From employees;

Output:-
First_name                         Salary
Abel				    24000
Rambo			    12000

Here we use Select statement to select the columns first_name and last_name to retrieve the information.

Insert command

After creating a table by using DDL language the main task is ti full the data into the created table the DML  insert command is used to insert a row in the table. 

Syntax of Insert Command:-

Insert Into [Table_name] values (column_value1,column_value2);

For example:-

NameNullType
 STUDENT_ID                         NOT NULL   NUMBER(10)
 STUDENT_NAME   CHAR(20)
 BRANCH_ID    VARCHAR2(10)
STUDENT_NO     

This is the predefined table insert the row inside the table.

Query:-
Insert into students Values(101,'Abhishek','civil',123456);
Insert into students Values(102,'Sahil','mech',78912)
Output:-
STUDENT_ID STUDENT_NAME         BRANCH_ID  STUDENT_NO
       101 		Abhishek            		 civil          123456
       102 		Sahil               		 mech            78912

Update Command

The update command is used to change values that already exist in a table.

NameNullType
 STUDENT_ID                         NOT NULL   NUMBER(10)
 STUDENT_NAME   CHAR(20)
 BRANCH_ID    VARCHAR2(10)
STUDENT_NO     

After adding some information if you want to update the records or change that time you have to use update command.

Syntax of update command:-

UPDATE table

SET column_name = value [column = value …]

[WHERE condition];

For example:-

Data in a table :-

STUDENT_IDSTUDENT_NAME   BRANCH_IDSTUDENT_NO
101AbhishekCivil 123456
102Sahil    Mech   78912

Update the branch_id=civil  to branch_id=ctech ?

Update students
set branch_id='ctech'
where branch_id='civil';
Output:-
STUDENT_ID STUDENT_NAME         BRANCH_ID  STUDENT_NO
       101 		Abhishek            		ctech        123456
       102 		Sahil               		 mech            78912

Here we update the existing value in the table.

DELETE Command

Delete command is used to delete some specific rows followed by the condition which we pass in the where clause from the table.

Syntax of Delete command

Delete From table _name 

where condition;

For example:

Data in a table:

STUDENT_IDSTUDENT_NAME   BRANCH_IDSTUDENT_NO
101AbhishekCivil 123456
102Sahil    Mech   78912

Delete the record who have a student_id 101. ?

SQL> Delete from Students
  2  wherestudent_id =101;
Output:- 1 row deleted.

STUDENT_ID STUDENT_NAME         BRANCH_ID  STUDENT_NO
102 		Sahil               		 mech            78912

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