根据条件 Sql 服务器更新了 table？

Question

我有以下代码：

-- First Table:  
UPDATE     [H$Agency Header]
SET        [Booking Rating] = '1' --!!!!! CONDTION HERE !!!!!
FROM       [H$Agency Header] AH
INNER JOIN #RatingLines   RL1
ON         RL1.[B_KEY] = AH.[Reservation No_]
WHERE      RL1.[RTD_COMMENT] <> ''-- If the Booking have a comment inDB2
AND        [Booking Rating] = '0'    -- Get only Booking without Comments

如您所见，如果内部联接在两个表 [H$Agency Header] 和 #RatingLines 中找到公共行，我将预订评级设置为 1。现在我想说，如果您没有找到它，请将其设置为“0”。我可以在 SET 命令旁边加上条件吗？怎么样？

Answer 1

假设上面的查询解析，那么你可以用 LEFT JOIN 和 CASE 做你想做的事。这需要将评论的条件从 where 移动到 on 子句：

UPDATE AH
    SET [Booking Rating] = (CASE WHEN RLI.B_KEY IS NULL THEN '0' ELSE '1' END)
    FROM [H$Agency Header] AH LEFT JOIN
         #RatingLines RL1
         ON RL1.[B_KEY] = AH.[Reservation No_] AND
            RL1.[RTD_COMMENT] <> ''-- If the Booking have a comment inDB2
    WHERE AH.[Booking Rating] = '0'    -- Get only Booking without Comments

注意：如果 [Booking Rating] 是整数，则不应将 0 和 1 放在单引号中。虽然它有效，但将数字列设置为字符串值会产生误导。

Answer 2

你可以这样写：

-- First Table:  
UPDATE     [H$Agency Header]
SET        [Booking Rating] = 
(case when RL1.[B_KEY] is null then '0' -- no match found
else '1'
end )
FROM       [H$Agency Header] AH
left  JOIN RatingLines   RL1 -- change join to Left
ON         RL1.[B_KEY] = AH.[Reservation No_] and  RL1.[RTD_COMMENT] <> ''
--WHERE      RL1.[RTD_COMMENT] <> ''-- If the Booking have a comment inDB2
--AND        [Booking Rating] = '0'

DEMO

根据条件 Sql 服务器更新了 table？

Updated a table based on a condtion Sql server?

sql

sql-server

set

sql-update