如何防止SQL多连接行错误并为多行应用值？

Question

ERROR [HY000] ERROR: Update canceled: attempt to update a target row with values from multiple join rows

有没有办法避免这个错误并更新包含E的每一行，尽管有多个连接行？

UPDATE V 
SET 
V.S = M.S, 
V.T = M.T, 
V.U = M.U 
FROM MAP M 
WHERE AND V.E = M.E; 

Answer 1

您需要按E获取一个值。我会尝试使用row_number()：

UPDATE V 
    SET V.S = M.S, 
     V.T = M.T, 
     V.U = M.U 
    FROM (SELECT M.*, ROW_NUMBER() OVER (PARTITION BY E ORDER BY E) as seqnum 
      FROM MAP M 
     ) M 
    WHERE V.E = M.E AND seqnum = 1; 

但是，您可能有其他的逻辑从要用于更新MAP选择特定值。