DROP TABLE (Transact-SQL)

Artikkeli
11/19/2024

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) Warehouse in Microsoft Fabric

Removes one or more table definitions and all data, indexes, triggers, constraints, and permission specifications for those tables. Any view or stored procedure that references the dropped table must be explicitly dropped by using DROP VIEW or DROP PROCEDURE. To report the dependencies on a table, use sys.dm_sql_referencing_entities.

Transact-SQL syntax conventions

Syntax

-- Syntax for SQL Server, Azure SQL Database, Warehouse in Microsoft Fabric
  
DROP TABLE [ IF EXISTS ] { database_name.schema_name.table_name | schema_name.table_name | table_name } [ ,...n ]  
[ ; ]

-- Syntax for Azure Synapse Analytics and Parallel Data Warehouse
  
DROP TABLE { database_name.schema_name.table_name | schema_name.table_name | table_name }
[;]

Arguments

database_name
Is the name of the database in which the table was created.

Azure SQL Database supports the three-part name format database_name.[schema_name].object_name when the database_name is the current database or the database_name is tempdb and the object_name starts with #. Azure SQL Database does not support four-part names.

IF EXISTS
Applies to: SQL Server ( SQL Server 2016 (13.x) through current version).

Conditionally drops the table only if it already exists.

schema_name
Is the name of the schema to which the table belongs.

table_name
Is the name of the table to be removed.

Remarks

DROP TABLE cannot be used to drop a table that is referenced by a FOREIGN KEY constraint. The referencing FOREIGN KEY constraint or the referencing table must first be dropped. If both the referencing table and the table that holds the primary key are being dropped in the same DROP TABLE statement, the referencing table must be listed first.

Multiple tables can be dropped in any database. If a table being dropped references the primary key of another table that is also being dropped, the referencing table with the foreign key must be listed before the table holding the primary key that is being referenced.

When a table is dropped, rules or defaults on the table lose their binding, and any constraints or triggers associated with the table are automatically dropped. If you re-create a table, you must rebind the appropriate rules and defaults, re-create any triggers, and add all required constraints.

If you delete all rows in a table by using DELETE tablename or use the TRUNCATE TABLE statement, the table exists until it is dropped.

Large tables and indexes that use more than 128 extents are dropped in two separate phases: logical and physical. In the logical phase, the existing allocation units used by the table are marked for deallocation and locked until the transaction commits. In the physical phase, the IAM pages marked for deallocation are physically dropped in batches.

If you drop a table that contains a VARBINARY(MAX) column with the FILESTREAM attribute, any data stored in the file system will not be removed.

When a ledger table is dropped, its dependent objects (the history table and the ledger view) are also dropped. A history table or a ledger view cannot be dropped directly. The system enforces a soft-delete semantics when dropping ledger tables and its dependent objects – they are not really dropped, but instead they are marked as dropped in system catalog views and renamed. For more information, see Ledger considerations and limitations.

Important

DROP TABLE and CREATE TABLE should not be executed on the same table in the same batch. Otherwise an unexpected error may occur.

In Fabric SQL database, dropping a table will drop it both from the database, as well as from Fabric OneLake- all mirrored data for the dropped table will be removed.

Permissions

Requires ALTER permission on the schema to which the table belongs, CONTROL permission on the table, or membership in the db_ddladmin fixed database role.

If the statement drops a ledger table, ALTER LEDGER permission is required.

Examples

A. Dropping a table in the current database

The following example removes the ProductVendor1 table and its data and indexes from the current database.

DROP TABLE ProductVendor1 ;

B. Dropping a table in another database

The following example drops the SalesPerson2 table in the AdventureWorks2022 database. The example can be executed from any database on the server instance.

DROP TABLE AdventureWorks2022.dbo.SalesPerson2 ;

C. Dropping a temporary table

The following example creates a temporary table, tests for its existence, drops it, and tests again for its existence. This example does not use the IF EXISTS syntax which is available beginning with SQL Server 2016 (13.x).

CREATE TABLE #temptable (col1 INT);  
GO  
INSERT INTO #temptable  
VALUES (10);  
GO  
SELECT * FROM #temptable;  
GO  
IF OBJECT_ID(N'tempdb..#temptable', N'U') IS NOT NULL   
DROP TABLE #temptable;  
GO  
--Test the drop.  
SELECT * FROM #temptable;

D. Dropping a table using IF EXISTS

Applies to: SQL Server ( SQL Server 2016 (13.x) through current version).

The following example creates a table named T1. Then the second statement drops the table. The third statement performs no action because the table is already deleted, however it does not cause an error.

CREATE TABLE T1 (Col1 INT);  
GO  
DROP TABLE IF EXISTS T1;  
GO  
DROP TABLE IF EXISTS T1;

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