PG - UPDATE SET FROM

写法 1

b 是单表

UPDATE a SET a.a1=b.b1,a.a2=b.b2 FROM b
WHERE b1=1 AND a1=1

写法 2

b 是子查询

UPDATE a SET a.a1=b.b1,a.a2=b.b2 FROM (
 SELECT * FROM t
    WHERE t.id = 1
) b
WHERE b1=1 AND a1=1