使用许多更新语句重构PostgreSQL WITH查询

Question

我有一个需要按顺序执行的SQL查询字符串，并且每个查询都需要一个WITH查询。事情是这样的：

WITH diff AS (
    SELECT NOW() - created_at as time_diff FROM table_a ORDER BY created_at DESC LIMIT 1 
) 
UPDATE table_x SET created_at = created_at + (SELECT time_diff FROM diff); 

WITH diff AS (
    SELECT NOW() - created_at as time_diff FROM table_a ORDER BY created_at DESC LIMIT 1 
) 
UPDATE table_y SET created_at = created_at + (SELECT time_diff FROM diff); 

WITH diff AS (
    SELECT NOW() - created_at as time_diff FROM table_a ORDER BY created_at DESC LIMIT 1 
) 
UPDATE table_a SET created_at = created_at + (SELECT time_diff FROM diff); 

这是一个稍微人为的例子，但我们的目的是“移动”的若干表的所有记录的created_at时间戳。由于table_a包含在所有WITH查询中，因此它必须是要更新的最后一个表或其他所有内容都是错误的。

理想我只想做这样的事情：

WITH diff AS (
    SELECT NOW() - created_at as time_diff FROM table_a ORDER BY created_at DESC LIMIT 1 
) 
UPDATE table_x SET created_at = created_at + (SELECT time_diff FROM diff) 
UPDATE table_y SET created_at = created_at + (SELECT time_diff FROM diff) 
UPDATE table_a SET created_at = created_at + (SELECT time_diff FROM diff); 

两个，因为它更简洁，因为这样的顺序将没有真正的问题。但这显然不是合法的语法。

有没有办法在单个查询中完成此操作？

Answer 1

你需要把每一次更新（除了最后一个）在CTE：

WITH diff AS (
    SELECT NOW() - created_at as time_diff FROM table_a ORDER BY created_at DESC LIMIT 1 
), upd_x as (
    UPDATE table_x SET created_at = created_at + (SELECT time_diff FROM diff) 
), upd_y as (
    UPDATE table_y SET created_at = created_at + (SELECT time_diff FROM diff) 
) 
UPDATE table_a SET created_at = created_at + (SELECT time_diff FROM diff);