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这篇文章主要讲解了“PostgreSQL 数据库中如何从 update 返回 old”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着丸趣 TV 小编的思路慢慢深入，一起来研究和学习“PostgreSQL 数据库中如何从 update 返回 old”吧！
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_id
RETURNING 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 .感谢各位的阅读，以上就是“PostgreSQL 数据库中如何从 update 返回 old”的内容了，经过本文的学习后，相信大家对 PostgreSQL 数据库中如何从 update 返回 old 这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是丸趣 TV，丸趣 TV 小编将为大家推送更多相关知识点的文章，欢迎关注！
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