DELETE

7 SQL - Language Statements

DELETE

delete rows of a table

    [ WITH [ RECURSIVE ] with_query [, ...] ]
    DELETE FROM [ ONLY ] table_name [ * ]
        [ FOR PORTION OF range_column_name for_portion_of_target ]
        [ [ AS ] alias ]
        [ USING from_item [, ...] ]
        [ WHERE condition | WHERE CURRENT OF cursor_name ]
        [ RETURNING [ WITH ( { OLD | NEW } AS output_alias [, ...] ) ]
                    { * | output_expression [ [ AS ] output_name ] } [, ...] ]

    where for_portion_of_target is:

    { FROM start_time TO end_time |
      ( portion ) }

## 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.

`TRUNCATE` provides a faster mechanism to remove all rows from a 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 row actually deleted. Any expression using the table's columns, and/or columns of other tables mentioned in `USING`, can be computed. The syntax of the `RETURNING` list is identical to that of the output list of `SELECT`.

If the `FOR PORTION OF` clause is used, the delete will only affect rows that overlap the given portion. Furthermore, if a row's application time extends outside the `FOR PORTION OF` bounds, then the delete will only change the application time within those bounds. In effect, only the history targeted by `FOR PORTION OF` is deleted, and no moments outside. Furthermore, after a row is deleted, new temporal leftovers might be inserted: rows whose range or multirange receives the remaining application time outside the targeted bounds, with the original values in their other columns. For range columns, there will be zero to two inserted records, depending on whether the original application time was completely deleted, extended before/after the change, or both. Multiranges never require two temporal leftovers, because one value can always contain whatever application time remains.

You must have the `DELETE` privilege on the table to delete from it, as well as the `SELECT` privilege for any table in the `USING` clause or whose values are read in the `condition`. When `FOR PORTION OF` is used, the secondary inserts do not require `INSERT` privilege on the table. (This is because conceptually no new information is being added; the inserted rows only preserve existing data about the untargeted time period.)

## 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 queries-with and sql-select for details.

`table_name`

- The name (optionally schema-qualified) of the table to delete rows from. If `ONLY` is specified before the table name, matching rows are deleted from the named table only. If `ONLY` is not specified, matching rows are also deleted from any tables inheriting from the named table. Optionally, `*` can be specified after the table name to explicitly indicate that descendant tables are included.

`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`.

`range_column_name`

- The range or multirange column to use when performing a temporal delete.

`for_portion_of_target`

- The portion to delete. If targeting a range column, this can be in the form `FROM` `start_time` `TO` `end_time`. Otherwise, it must be in the form `(``portion``)`, where `portion` is an expression that yields a value of the same type as `range_column_name`.

`start_time`

- The earliest time (inclusive) to change in a temporal delete. This must be a value matching the base type of the range from `range_column_name`. A null value here indicates a delete whose beginning is unbounded (as with range types).

`end_time`

- The latest time (exclusive) to change in a temporal delete. This must be a value matching the base type of the range from `range_column_name`. A null value here indicates a delete whose end is unbounded (as with range types).

`from_item`

- A table expression allowing columns from other tables to appear in the `WHERE` condition. This uses the same syntax as the `FROM` clause of a `SELECT` statement; for example, an alias for the table name can be specified. Do not repeat the target table as a `from_item` unless you wish to set up a self-join (in which case it must appear with an alias in the `from_item`).

`condition`

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

`cursor_name`

- The name of the cursor to use in a `WHERE CURRENT OF` condition. The row to be deleted is the one most recently fetched from this cursor. The cursor must be a non-grouping query on the `DELETE`'s target table. Note that `WHERE CURRENT OF` cannot be specified together with a Boolean condition. See sql-declare for more information about using cursors with `WHERE CURRENT OF`.

`output_alias`

- An optional substitute name for `OLD` or `NEW` rows in the `RETURNING` list.

  By default, old values from the target table can be returned by writing `OLD.`column_name`` or `OLD.*`, and new values can be returned by writing `NEW.`column_name`` or `NEW.*`. When an alias is provided, these names are hidden and the old or new rows must be referred to using the alias. For example `RETURNING WITH (OLD AS o, NEW AS n) o.*, n.*`.

`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.

  A column name or `*` may be qualified using `OLD` or `NEW`, or the corresponding `output_alias` for `OLD` or `NEW`, to cause old or new values to be returned. An unqualified column name, or `*`, or a column name or `*` qualified using the target table name or alias will return old values.

  For a simple `DELETE`, all new values will be `NULL`. However, if an `ON DELETE` rule causes an `INSERT` or `UPDATE` to be executed instead, the new values may be non-`NULL`.

`output_name`

- A name to use for a returned column.

## Outputs

On successful completion, a `DELETE` command returns a command tag of the form

    DELETE count

The `count` is the number of rows deleted. Note that the number may be less than the number of rows that matched the `condition` when deletes were suppressed by a `BEFORE DELETE` trigger. If `count` is 0, no rows were deleted by the query (this is not considered an error). If `FOR PORTION OF` was used, the `count` does not include temporal leftovers that were inserted.

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. If `FOR PORTION OF` was used, the `RETURNING` clause gives one result for each deleted row, but does not include inserted temporal leftovers. The value of the application-time column matches the old value of the deleted row(s). Note this will represent more application time than was actually erased, if temporal leftovers were inserted.

## Notes

PostgreSQL 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');

In some cases the join style is easier to write or faster to execute than the sub-select style.

When `FOR PORTION OF` is used, this can result in users who don't have `INSERT` privileges firing `INSERT` triggers. This should be considered when using `SECURITY DEFINER` trigger functions.

## 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 *;

Delete the row of tasks on which the cursor `c_tasks` is currently positioned:

    DELETE FROM tasks WHERE CURRENT OF c_tasks;

An example of a temporal delete:

    DELETE FROM products
      FOR PORTION OF valid_at FROM '2021-08-01' TO '2023-09-01'
      WHERE product_no = 5;

While there is no `LIMIT` clause for `DELETE`, it is possible to get a similar effect using the same method described in the documentation of `UPDATE`:

    WITH delete_batch AS (
      SELECT l.ctid FROM user_logs AS l
        WHERE l.status = 'archived'
        ORDER BY l.creation_date
        FOR UPDATE
        LIMIT 10000
    )
    DELETE FROM user_logs AS dl
      USING delete_batch AS del
      WHERE dl.ctid = del.ctid;

This use of ctid is only safe because the query is repeatedly run, avoiding the problem of changed ctids.

## Compatibility

This command conforms to the SQL standard, except that the `USING` and `RETURNING` clauses are PostgreSQL extensions, as is the ability to use `WITH` with `DELETE`.

## See Also

- sql-truncate