SQL Commands:
SQL commands are instructions used to communicate with the database
to perform specific task that work with data. SQL commands can be used
not only for searching the database but also to perform various other
functions like, for example, you can create tables, add data to tables,
or modify data, drop the table, set permissions for users. SQL commands
are grouped into four major categories depending on their functionality:
1.Data Definition Language (DDL) - These SQL
commands are used for creating, modifying, and dropping the structure of
database objects. The commands are CREATE, ALTER, DROP, RENAME, and
TRUNCATE.
| Command | Description |
|---|---|
| CREATE | Creates a new table, a view of a table, or other object in database |
| ALTER | Modifies an existing database object, such as a table. |
| DROP | Deletes an entire table, a view of a table or other object in the database. |
2.Data Manipulation Language (DML) - These SQL
commands are used for storing, retrieving, modifying, and deleting data.
These commands are SELECT, INSERT, UPDATE, and DELETE.
| Command | Description |
|---|---|
| INSERT | Creates a record |
| UPDATE | Modifies records |
| DELETE | Deletes records |
3.Data Control Language (DCL) - These SQL commands are used for providing security to database objects. These commands are GRANT and REVOKE.
| Command | Description |
|---|---|
| GRANT | Gives a privilege to user |
| REVOKE | Takes back privileges granted from user |
4.Transaction Control Language (TCL) - These SQL commands are used for managing changes affecting the data. These commands are COMMIT, ROLLBACK, and SAVEPOINT.
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