Database languages

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Database languages are used to create and maintain databases in a system. The following languages are used in the database.

DDL

The full name of DDL is the data definition language. This is used to define a conceptual schema and it also gives information about how this schema is implemented in physical devices.

The most important DDL statements in SQL are the following:

1. CREATE: – To create objects in database.

2. ALTER: – To change the structure of the database.

3. DROP: – to delete objects from the database.

4. COMMENT: – To add comments to the data dictionary.

5. RENAME: – To rename (change in name) of the object.

DML                                                                      

The full name of DML is a data manipulation language. And the language that is used to manipulate the data in the database is called the language DML.

Following are some examples of this: –

1. SELECT: – Retrieve data from a database.

2. INSERT: – Inserting data in a table.

3. UPDATE: – To update the existing data in the table.

4. DELETE: – To delete all the records from the table.

5. CALL: – To call java subprogram.

6. LOCK TABLE: – To control concurrency.

DCL: –

The full name of DCL is called data control language. DCL is used to control access to the data stored in the database.

The following are some examples of this.

1. GRANT: – To grant privilege to users for the database.

2. REVOKE: – REVOKE command is used to withdraw the privilege granted by GRANT command.

VDL: –

• Its full name is view definition language (view definition language).

• This language is used to specify user views and their mapping in the conceptual schema.

• It defines the subset of records available for classes of users.

• It creates virtual tables and makes the users see the view as a conceptual level.

• VDL specifies the user interface.

SDL: –

• The full name of SDL is storage definition language (storage definition language).

• It specifies the mapping between two schemas.

• It is used to specify an internal schema.


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