帶有case語句的另一個表的UPDATE表

Question

我目前遇到了問題。 我需要根據這個條件更新表B中的表A：

• 如果表A中的一個記錄為空（例如名稱），則從表B更新該記錄

這是我從頭腦中想到的錯誤驅動腳本。 這就是我想要發生的事情。

UPDATE TableA
   SET 
      NAME =
      (
         CASE WHEN TableA.NAME IS NULL THEN
            SELECT TableB.NAME
            FROM TableB
            WHERE TableB._ID = 1
      ),
      ADDRESS =
      (
         CASE WHEN TableA.ADDRESS IS NULL THEN
            SELECT TableB.ADDRESS
            FROM TableB
            WHERE TableB._ID = 1
      )
   WHERE TableA._ID = 1

這樣的事情。 有任何想法嗎？

Answer 1

您可以將表連接在一起，並在TableA為null時使用IsNull回退到TableB：

update  a
set     name = IsNull(a.name, b.name)
,       address = IsNull(a.address, b.address)
from    TableA as a
inner join
        TableB as b
on      a._ID = b._ID

Answer 2

嘗試這個 -

update a
SET a.name = ( CASE WHEN a.name IS NULL THEN b.name ELSE a.name END ),
    a.address = ( CASE WHEN a.address IS NULL THEN b.address ELSE a.address END )
FROM tableA as a, tableB as b
where a.ID = b.ID

Answer 3

您可能會發現使用兩個語句更容易......

UPDATE TableA
    SET NAME = (SELECT NAME
                    FROM TableB
                    WHERE TableA.ID = TableB.ID)
    WHERE NAME IS NULL;

UPDATE TableA
    SET ADDRESS = (SELECT ADDRESS
                       FROM TableB
                       WHERE TableA.ID = TableB.ID)
    WHERE ADDRESS IS NULL;