H2 Database - Drop


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DROP is a command taken from the generic SQL grammar. This command is used to delete a database component and its structure from the memory. There are different scenarios with the Drop command that we will discuss in this chapter.

Drop Table

Drop Table is a command that deletes the respective table and its structure.

Syntax

Following is the generic syntax of the Drop Table command.

DROP TABLE [ IF EXISTS ] tableName [,...] [ RESTRICT | CASCADE ]

The command will fail if we are using RESTRICT and the table having dependent views exist. All dependent views are dropped, when we are using CASCADE keyword.

Example

In this example, we will drop a table named test using the following query.

DROP TABLE test;

The above query produces the following output.

(6) row (s) effected 

Drop Schema

Drop Schema is a command that drops a respective schema from the database server. It will not work from the current schema.

Syntax

DROP SCHEMA [ IF EXISTS ] schemaName 

Example

In this example, we will drop a schema named test_schema using the following query.

DROP SCHEMA TEST_SCHEMA; 

The above query produces the following output.

(0) row(s) effected

Drop Sequence

Drop Sequence is a command used to drop a sequence from the table structure.

Syntax

Following is the generic syntax of the Drop Sequence command.

DROP SEQUENCE [ IF EXISTS ] sequenceName

This command commits an open transaction in this connection.

Example

In this example, we will drop a sequence named sequence_id. Following is the command.

DROP SEQUENCE sequence_id;

The above command produces the following output.

(0) row (s) effected 

Drop View

Drop View is a command used to drop the existing view. All dependent views are dropped as well if the CASCADE clause is used.

Syntax

Following is the generic syntax of the Drop View command.

DROP VIEW [ IF EXISTS ] viewName [ RESTRICT | CASCADE ]

Example

In this example, we will drop a view named sample_view using the following query.

DROP VIEW sample_view;

The above query produces the following output.

(0) row (s) effected 


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