PostgreSQL数据库中如何从update返回old

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UPDATE tbl xSET    tbl_id = 23     , name = 'New Guy'FROM   tbl y                -- using the FROM clauseWHERE  x.tbl_id = y.tbl_id  -- must be UNIQUE NOT NULLAND    x.tbl_id = 3RETURNING y.tbl_id AS old_id, y.name AS old_name        , x.tbl_id          , x.name;

 old_id | old_name | tbl_id |  name--------+----------+--------+---------  3     | Old Guy  | 23     | New Guy

 WITH sel AS (

   SELECT tbl_id, name FROM tbl WHERE tbl_id = 3  -- assuming unique tbl_id   ), upd AS (   UPDATE tbl SET name = 'New Guy' WHERE tbl_id = 3   RETURNING tbl_id, name   )SELECT s.tbl_id AS old_id, s.name As old_name     , u.tbl_id, u.nameFROM   sel s, upd u;

UPDATE tbl xSET    tbl_id = 24     , name = 'New Gal'FROM  (SELECT tbl_id, name FROM tbl WHERE tbl_id = 4 FOR UPDATE) y WHERE  x.tbl_id = y.tbl_idRETURNING y.tbl_id AS old_id, y.name AS old_name, x.tbl_id, x.name;对于 insert  怎么办呢 ?

WITH sel AS (   SELECT id, title   FROM   posts   WHERE  id IN (1,2)   -- select rows to copy   ),    ins AS (   INSERT INTO posts (title)   SELECT title FROM sel   RETURNING id, title )SELECT ins.id, sel.id AS from_idFROM   insJOIN   sel USING (title);If title is not unique per query (but at least id is unique per table):WITH sel AS (   SELECT id, title, row_number() OVER (ORDER BY id) AS rn   FROM   posts   WHERE  id IN (1,2)   -- select rows to copy   ORDER  BY id   ),    ins AS (   INSERT INTO posts (title)   SELECT title FROM sel ORDER  BY id  -- ORDER redundant to be sure   RETURNING id )SELECT i.id, s.id AS from_idFROM  (SELECT id, row_number() OVER (ORDER BY id) AS rn FROM ins) iJOIN   sel s USING (rn);This second query relies on the undocumented implementation detail that rows are inserted in the order provided. It works in all current versions of Postgres and is probably not going to break.留着做参考吧 .

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