DELETE

— delete rows of a table

Synopsis

[ WITH [RECURSIVE] <with_query> [, ...] ]
DELETE FROM <table_name> [ [AS] <alias> ]
[ USING <using_list> ]
[ WHERE <condition> ]
[ RETURNING { * | <output_expression> [AS <output_name>]} [, ...] ]

Description

DELETE deletes rows that satisfy the WHERE clause from the specified table. If the WHERE clause is absent, the effect is to delete all rows in the table. The result is a valid, but empty table.

There are two ways to delete rows in a table using information contained in other tables in the database: using sub-selects, or specifying additional tables in the USING clause. Which technique is more appropriate depends on the specific circumstances.

The optional RETURNING clause causes DELETE to compute and return value(s) based on each deleted row. Any expression using the table's columns, and/or columns of other tables mentioned in the USING clause, can be computed. The syntax of the RETURNING list is identical to that of the output list of SELECT.

Parameters

<with_query>

The WITH clause allows you to specify one or more subqueries that can be referenced by name in the DELETE query. See SELECT for details.

<table_name>

The name (optionally schema-qualified) of the table to delete rows from.

<alias>

A substitute name for the target table. When an alias is provided, it completely hides the actual name of the table. For example, given DELETE FROM foo AS f, the remainder of the DELETE statement must refer to this table as f not foo.

<using_list>

A list of table expressions, allowing columns from other tables to appear in the WHERE condition. This is similar to the list of tables that can be specified in the FROM clause of a SELECT statement; for example, an alias for the table name can be specified. Do not repeat the target table in the <using_list>, unless you wish to set up a self-join.

<condition>

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

<output_expression>

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 named by <table_name> or table(s) listed in USING. Write * to return all columns.

<output_name>

A name to use for a returned column.

Outputs

If the DELETE command contains a RETURNING clause, the result will be similar to that of a SELECT statement containing the columns and values defined in the RETURNING list, computed over the row(s) deleted by the command.

Referring to other tables

Hyper lets you reference columns of other tables in the WHERE condition by specifying the other tables in the USING clause. For example, to delete all films produced by a given producer, one can do:

DELETE FROM films USING producers
  WHERE producer_id = producers.id AND producers.name = 'foo';

What is essentially happening here is a join between films and producers, with all successfully joined films rows being marked for deletion. This syntax is not standard. A more standard way to do it is:

DELETE FROM films
  WHERE producer_id IN (SELECT id FROM producers WHERE name = 'foo');

The query plans generated for both forms are equivalent. Thus, they do not differ in terms of performance.

Examples

Delete all films but musicals:

DELETE FROM films WHERE kind <> 'Musical';

Clear the table films:

DELETE FROM films;

Delete completed tasks, returning full details of the deleted rows:

DELETE FROM tasks WHERE status = 'DONE' RETURNING *;

Compatibility

This command conforms to the SQL standard, except that the USING and RETURNING clauses are Hyper extensions (also available in PostgreSQL), as is the ability to use WITH with DELETE.