Postgresql:更新问题

我想做一些更新，逻辑上如下所示-

UPDATE    t1 
SET       (x1, x2) = (SELECT  x1, x2 
                              FROM    t1 
                              WHERE id_1 = 8 
                              AND id_2 =1 
                              AND id_3 = 3)
;

但从表面上看，这些类型的更新目前似乎没有在Postgresql中实现。除了经典样式（我所说的经典是指

设置x1=value1，x2=value2，…

样式）之外，这个问题还有其他解决方法吗？

您可以这样做：

UPDATE t1 SET x1 = a.x1, x2 = a.x2 FROM 
   (SELECT x1, x2 FROM t1 WHERE id_1 = 8 AND id_2 = 1 AND id_3 = 3) AS a

可能需要其他条件：

UPDATE t1 SET x1 = a.x1, x2 = a.x2 FROM 
   (SELECT id, x1, x2 FROM t1 WHERE id_1 = 8 AND id_2 = 1 AND id_3 = 3) AS a 
   WHERE a.id = t1.id