Postgresql 中文操作指南
Synopsis
[ WITH [ RECURSIVE ] with_query [, ...] ]
DELETE FROM [ ONLY ] table_name [ * ] [ [ AS ] alias ]
[ USING from_item [, ...] ]
[ WHERE condition | WHERE CURRENT OF cursor_name ]
[ RETURNING * | output_expression [ [ AS ] output_name ] [, ...] ]Description
DELETE 从指定表中删除满足 WHERE 子句的行。如果 WHERE 子句不存在，则删除表中的所有行。结果是一个有效但为空的表。
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.
Tip
TRUNCATE 提供了一种更快的机制来从表中删除所有行。
TRUNCATE provides a faster mechanism to remove all rows from a table.
有两种方法可以使用数据库中其他表中包含的信息来删除表中的行：使用子选择或在 USING 子句中指定其他表。哪种技术更合适取决于具体情况。
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.
可选的 RETURNING 子句会导致 DELETE 计算并返回基于实际删除的每一行的值。可以使用表列和/或 USING 中提到的其他表的列的任何表达式来计算。 RETURNING 列表的语法与 SELECT 的输出列表相同。
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.
您必须对要从中删除行的表具有 DELETE 特权，以及 USING 子句中或在 condition 中读取其值的任何表的 SELECT 特权。
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.
Parameters
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with_query
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The WITH clause allows you to specify one or more subqueries that can be referenced by name in the DELETE query. See Section 7.8 and SELECT for details.
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table_name
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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.
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alias
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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.
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from_item
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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).
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condition
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An expression that returns a value of type boolean. Only rows for which this expression returns true will be deleted.
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cursor_name
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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 DECLARE for more information about using cursors with WHERE CURRENT OF.
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output_expression
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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.
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output_name
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A name to use for a returned column.
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Outputs
成功完成后， DELETE 命令会返回以下形式的命令标记
On successful completion, a DELETE command returns a command tag of the form
DELETE countcount 是删除的行数。注意，当删除操作被 BEFORE DELETE 触发器禁止时，此数字可能小于与 condition 匹配的行数。如果 count 为 0，则该查询未删除任何行（这不会视为错误）。
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).
如果 DELETE 命令包含一个 RETURNING 子句，则结果将类似于包含由命令删除的行上计算得出的 RETURNING 列表中定义的列和值，且包含 SELECT 语句的结果。
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.
Notes
通过在 USING 子句中指定其他表，PostgreSQL 允许您在 WHERE 条件中引用其他表的列。例如，若要删除某个指定制作人制作的所有电影，则可以执行以下操作：
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';这里实际上发生了 films 和 producers 之间的联接，所有成功联接的 films 行都会被标记为要删除。此语法不是标准的。一种更标准的方法是：
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');在某些情况下，联接类型比子选择类型更易于编写或执行速度更快。
In some cases the join style is easier to write or faster to execute than the sub-select style.
Examples
删除所有非音乐剧电影：
Delete all films but musicals:
DELETE FROM films WHERE kind <> 'Musical';清空表 films ：
Clear the table films:
DELETE FROM films;删除已完成任务，并返回已删除行的详细信息：
Delete completed tasks, returning full details of the deleted rows:
DELETE FROM tasks WHERE status = 'DONE' RETURNING *;删除游标 c_tasks 当前位于其上的 tasks 行：
Delete the row of tasks on which the cursor c_tasks is currently positioned:
DELETE FROM tasks WHERE CURRENT OF c_tasks;