Learn Data Manipulation Language (DML) with Examples

 

Data Manipulation Language (DML)

DML commands are used to inert new values into a table, updating, deleting and retrieving data. 

The most used commands are insert, update, delete and select. 

However select is the most popular and widely used. 

SQL Insert 

insert command is used to add new rows to a table

Syntax

      INSERT INTO Table_name (Col1, Col2, Col3, Col4, ... )
                    VALUES(value1,value2,value3,value4, ... )

Example:

 

  INSERT INTO employees (emp_id, emp_name, salary,dept_id)
  VALUES(1,'Ahmed',3000,1)

Insert a second record into employees table

Delete a record from employees table

Syntax:

DELETE FROM table_name;

Example: Delete employee with emp_id=2 from employees table

 

DELETE FROM employees WHERE emp_id = 2 

Note:

If we use the delete command without where clause will result in deleting all the data from the table.

Update Records

Syntax:

UPDATE table_name                      

SET column_name1 = new_value1,

column_value1 = new_value2, 

column_value N = new_value N

       WHERE column_name = condition_value; 

Example:

From the employees table above we would like to update the salary of the employee with emp_id =1 from 2000 to become 4000.

Note:

If we use the update command without where clause will result in updating all the data from the specified column.

 

Updating multiple columns with one update command:

Example:

From the employees table above we would like to update the salary to 5000 and dept_id to 2 for the employee with emp_id = 2.

 

UPDATE employees

SET salary = 5000,

dept_id = 2

       WHERE emp_id = 2;