SQL Data Manipulation Language (DML)

Introduction to DML

DML stands for Data Manipulation Language.
It is a language used for selecting, inserting, deleting and updating data in a database.
It is used to retrieve and manipulate data in a relational database.

DDL commands are as follows,

DML performs read-only queries of data.

1. SELECT COMMAND

SELECT command is used to retrieve data from the database.
This command allows database users to retrieve the specific information they desire from an operational database.
It returns a result set of records from one or more tables.

SELECT Command has many optional clauses are as stated below:

Clause	Description
WHERE	It specifies which rows to retrieve.
GROUP BY	It is used to arrange the data into groups.
HAVING	It selects among the groups defined by the GROUP BY clause.
ORDER BY	It specifies an order in which to return the rows.
AS	It provides an alias which can be used to temporarily rename tables or columns.

Syntax:
SELECT * FROM <table_name>;

Example : SELECT Command

SELECT * FROM employee;

OR

SELECT * FROM employee
where salary >=10,000;

2. INSERT COMMAND

INSERT command is used for inserting a data into a table.
Using this command, you can add one or more records to any single table in a database.
It is also used to add records to an existing code.

Syntax:
INSERT INTO <table_name> (`column_name1` <datatype>, `column_name2` <datatype>, . . . , `column_name_n` <database>) VALUES (`value1`, `value2`, . . . , `value n`);

Example:
INSERT INTO employee (`eid` int, `ename` varchar(20), `city` varchar(20))
VALUES (`1`, `ABC`, `PUNE`);

3. UPDATE COMMAND

UPDATE command is used to modify the records present in existing table.
This command updates existing data within a table.
It changes the data of one or more records in a table.

Syntax:
UPDATE <table_name>
SET <column_name = value>
WHERE condition;

Example : UPDATE Command

UPDATE employee
SET salary=20000
WHERE ename='ABC';

4. DELETE COMMAND

DELETE command is used to delete some or all records from the existing table.
It deletes all the records from a table.

Syntax:

DELETE FROM <table_name> WHERE <condition>;

Example : DELETE Command

DELETE FROM employee
WHERE emp_id = '001';