UPDATE抱怨不止一個返回值

Question

我有這樣的數據結構：

request 
======= 
building_id 
lot_code 

building 
======== 
building_id 
lot_id 

lot 
=== 
lot_id 
lot_code 

的request表缺少的building_id列的值，我想從另一個表中填充它。所以，我已經試過這樣：

UPDATE request 
SET building_id = (
    SELECT bu.building_id 
    FROM building bu 
    INNER JOIN lot lo ON bu.lot_id=lo.lot_id 
    WHERE lo.lot_code = request.lot_code 
); 

但我發現了這個錯誤：

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

它是由於錯誤的語法？數據模型允許每個建築物有多個建築物，但實際數據不包含這種情況，因此每個lot_code最多應該有一個building_id。

Answer 1

可能你的意思

UPDATE request 
SET building_id = bu.building_id 
FROM building bu 
    INNER JOIN lot lo ON bu.lot_id=lo.lot_id 
WHERE lo.lot_code = request.lot_code 

Answer 2

在您的查詢中使用top 1，如下例所示。

 
UPDATE request 
SET building_id = (
    SELECT top 1 bu.building_id 
    FROM building bu 
    INNER JOIN lot lo ON bu.lot_id=lo.lot_id 
    WHERE lo.lot_code = request.lot_code 
);