DELETE

Function

Deletes rows that satisfy the WHERE clause from the specified table. If the WHERE clause does not exist, all rows in the table will be deleted. The result is a valid, but an empty table.

Precautions

• You must have the DELETE permission on the table to delete from it, as well as the SELECT permission for any table in the USING clause or whose values are read in the condition.
• For replication tables, DELETE can be performed only in the following two scenarios:
  • Scenarios with primary key constraints.
  • Scenario where the execution plan can be pushed down.
• For column-store tables, the RETURNING clause is currently not supported.

• Avoid using UPDATE or DELETE to modify or delete a large volume of data and use TRUNCATE PARTITION or DROP PARTITION instead.
• For more information about development and design specifications, see "GaussDB(DWS) Development and Design Proposal" in the Data Warehouse Service (DWS) Developer Guide.

Syntax

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[ WITH [ RECURSIVE ] with_query [, ...] ]
    DELETE [/*+ plan_hint */] FROM [ ONLY ] table_name [ * ] [ [ AS ] alias ]
    [ PARTITION ( partition_name ) | PARTITION FOR ( partition_key_value [, ...] ) ]
    [ USING using_list ]
    [ WHERE condition | WHERE CURRENT OF cursor_name ]
    [ RETURNING { * | { output_expr [ [ AS ] output_name ] } [, ...] } ];

Parameter Description

• WITH [ RECURSIVE ] with_query [, ...]

  The WITH clause allows you to specify one or more subqueries that can be referenced by name in the primary query, equal to temporary table.

  If RECURSIVE is specified, it allows a SELECT subquery to reference itself by name.

  The with_query detailed format is as follows:

  with_query_name [ ( column_name [, ...] ) ] AS
  ( {select | values | insert | update | delete} )

  -- with_query_name specifies the name of the result set generated by a subquery. Such names can be used to access the result sets of

  column_name specifies the column name displayed in the subquery result set.

  Each subquery can be a SELECT, VALUES, INSERT, UPDATE or DELETE statement.

• plan_hint clause

  Following the keyword in the /*+ */ format, hints are used to optimize the plan generated by a specified statement block. For details, see "GaussDB(DWS) Performance Tuning" > "SQL Tuning" > "Hint-based Tuning" in Data Warehouse Service (DWS) Developer Guide.

• ONLY

  If ONLY is specified, only that table is deleted. If ONLY is not specified, this table and all its sub-tables are deleted.

• table_name

  Specifies the name (optionally schema-qualified) of a target table.

  Value range: an existing table name

• alias

  Specifies the alias for the target table.

  Value range: a string. It must comply with the naming convention.

• partition_name

  Specifies the name of a partition. Only clusters of version 8.2.1 or later support this option.

  Value range: An existing partition name.

• partition_key_value

  Specifies the key value of a partition.

  The value specified by PARTITION FOR ( partition_key_value [, ...] ) can uniquely identify a partition.

  Value range: value range of the partition key for the partition to be renamed

• using_list

  Specifies the USING clause.

• condition

  Specifies an expression that returns a value of type boolean. Only rows for which this expression returns true will be deleted.

• WHERE CURRENT OF cursor_name

  Not supported currently. Only syntax interface is provided.

• output_expr

  Specifies an expression to be computed and returned by the DELETE command after each row is deleted. The expression can use any column names of the table. Write * to return all columns.

• output_name

  Specifies a name to use for a returned column.

  Value range: a string. It must comply with the naming convention.

Examples

Create the tpcds.customer_address_bak table:

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CREATE TABLE tpcds.customer_address_bak AS TABLE tpcds.customer_address;

Delete employees whose ca_address_sk is less than 14888 in the tpcds.customer_address_bak table:

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DELETE FROM tpcds.customer_address_bak WHERE ca_address_sk < 14888;

Delete the employees whose ca_address_sk is 14891, 14893, and 14895 from tpcds. customer_address_bak:

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DELETE FROM tpcds.customer_address_bak WHERE ca_address_sk in (14891,14893,14895);

Delete all data in the tpcds.customer_address_bak table:

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DELETE FROM tpcds.customer_address_bak;

Use a subquery (to delete the row-store table tpcds.warehouse_t30) to obtain a temporary table temp_t, and then query all data in the temporary table temp_t:

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WITH temp_t AS (DELETE FROM tpcds.warehouse_t30 RETURNING *) SELECT * FROM temp_t ORDER BY 1;

Delete partition p1 from the partitioned table test_range_row:

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CREATE TABLE test_range_row(a int, d int)
DISTRIBUTE BY hash(a) PARTITION BY RANGE(d)
(
    PARTITION p1 values LESS THAN (60),
    PARTITION p2 values LESS THAN (75),
    PARTITION p3 values LESS THAN (90),
    PARTITION p4 VALUES LESS THAN (maxvalue)
);
INSERT OVERWRITE INTO test_range_row PARTITION(p1) VALUES(55,51);
INSERT OVERWRITE INTO test_range_row PARTITION(p3) VALUES(85,80);

DELETE FROM test_range_row PARTITION(p1);