SQL 删除/插入行的 CTE 语法

Question

从 table 中 delete 的 CTE 语法是什么，然后 insert 到相同的 table 和return 插入?

的值

在 2 小时的睡眠中运行，有些东西看起来不对（除了这不会执行的事实）：

WITH delete_rows AS (
   DELETE FROM <some_table> WHERE id = <id_value>
   RETURNING *
)
SELECT * FROM delete_rows
UNION
(
   INSERT INTO <some_table> ( id, text_field )
      VALUES ( <id_value>, '<text_field_value>' )
      RETURNING *
)

预期的行为是首先清除某个 ID 的所有记录，然后插入相同 ID 的记录（故意不是更新插入）和 return 那些插入的记录（不是删除）。

Answer 1

您的问题更新明确表明您不能在单个语句中执行此操作。

打包到同一语句的 CTE 中，两个操作（INSERT 和 DELETE）将看到 table 的相同快照并在 处虚拟执行同时。即，INSERT 仍会看到您认为已经删除的所有行。 The manual:

All the statements are executed with the same snapshot (see Chapter 13), so they cannot "see" one another's effects on the target tables.

您可以将它们作为两个独立的语句包装到同一个事务中——这似乎也不是绝对必要的，但它会允许整个操作自动成功/失败：

BEGIN;

DELETE FROM <some_table> WHERE id = <id_value>;

INSERT INTO <some_table> (id, text_field)
VALUES ( <id_value>, '<text_field_value>')
RETURNING *;

COMMIT;

现在，INSERT可以看到DELETE的结果了。

Answer 2

CREATE TABLE test_table (value TEXT UNIQUE);
INSERT INTO test_table SELECT 'value 1';
INSERT INTO test_table SELECT 'value 2';

WITH delete_row AS (DELETE FROM test_table WHERE value='value 2' RETURNING 0)
  INSERT INTO test_table
    SELECT DISTINCT 'value 2' 
    FROM (SELECT 'dummy') dummy
    LEFT OUTER JOIN delete_row ON TRUE
    RETURNING *;

上面的查询处理了 DELETE 删除 0/1/一些行的情况。

Answer 3

详述 skif1979 的 "DelSert" CTE 方法，"Logged DelSert:"

-- setups
DROP TABLE IF EXISTS _zx_t1 ;

CREATE TEMP TABLE 
  IF NOT EXISTS 
     _zx_t1 
     ( id bigint
     , fld2 bigint
     , UNIQUE (id)
     );
-- unique records
INSERT INTO _zx_t1 SELECT 1, 99;
INSERT INTO _zx_t1 SELECT 2, 98;


WITH 
  _cte_del_row AS 
   (   DELETE 
       FROM _zx_t1 
       WHERE id = 2 
     RETURNING id as _b4_id, fld2 as _b4_fld2 -- returns complete deleted row
   )
 , _cte_delsert AS
     (  INSERT 
       INTO _zx_t1 
       SELECT DISTINCT 
          _cte_del_row._b4_id
        , _cte_del_row._b4_fld2 + 1 
        from (SELECT null::integer AS _zunk) _zunk  -- skif1979's trick here
             LEFT OUTER JOIN _cte_del_row         -- clever LOJ magic  
             ON TRUE                              -- LOJ cartesian product
        RETURNING id as _aft_id , fld2 as _aft_fld2 -- return newly "delserted" rows
       )
  SELECT * -- returns before & after snapshots from CTE's
  FROM 
   _cte_del_row
   , _cte_delsert ;

RESULT: _b4_id | _b4_fld2 | _aft_id | _aft_fld2 --------+----------+---------+----------- 2 | 209 | 2 | 210 </pre>

AFAICT 这些都是线性发生的 w/in 一个工作单元，类似于日志更新或日志更新。

适用于
- 子记录
- OR 无 FK 的模式
- 或带级联删除的 FK
不适用于
- 具有 FK 且无级联删除的父记录

Answer 4

一个相关的（和 IMO 更好的）答案，类似于 "Logged DelSert" 是这个，一个记录的 "SelUp" :

    -- setups
    DROP TABLE IF EXISTS _zx_t1 ;

    CREATE TEMP TABLE 
      IF NOT EXISTS 
         _zx_t1 
         ( id bigint
         , fld2 bigint
         , UNIQUE (id)
         );
    -- unique records
    INSERT INTO _zx_t1 SELECT 1, 99;
    INSERT INTO _zx_t1 SELECT 2, 98;


    WITH 
      _cte_sel_row AS 
       (   SELECT                 -- start unit of work with read
              id as _b4_id        -- fields need to be aliased 
             ,fld2 as _b4_fld2    -- to prevent ambiguous column errors
           FROM _zx_t1 
           WHERE id = 2
           FOR UPDATE 
       )
     , _cte_sel_up_ret AS           -- we're in the same UOW
       (  UPDATE _zx_t1             -- actual table
           SET fld2 = _b4_fld2 + 1  -- some actual work
          FROM  _cte_sel_row    
            WHERE id = _b4_id
               AND fld2 < _b4_fld2 + 1  -- gratuitous but illustrates the point 
          RETURNING id as _aft_id, fld2 as _aft_fld2
         ) 
    SELECT  
          _cte_sel_row._b4_id
         ,_cte_sel_row._b4_fld2         -- before
         ,_cte_sel_up_ret._aft_id  
         ,_cte_sel_up_ret._aft_fld2     -- after
       FROM _cte_sel_up_ret  
          INNER JOIN _cte_sel_row  
           ON TRUE AND _cte_sel_row._b4_id = _cte_sel_up_ret._aft_id
    ;

 RESULT: 
           _b4_id | _b4_fld2 | _aft_id | _aft_fld2 
          --------+----------+---------+-----------
                2 |      209 |       2 |       210
</pre> 

另请参阅：
https://rob.conery.io/2018/08/13/transactional-data-operations-in-postgresql-using-common-table-expressions/

SQL 删除/插入行的 CTE 语法

SQL CTE Syntax to DELETE / INSERT rows

sql

postgresql

common-table-expression

postgresql-9.2