我有以下SQL查询。
SELECT MIN(PLD.available_date) as 'FROM', MAX(PLD.available_date) as 'UNTIL', (
CASE
WHEN DATEDIFF('2012-04-01', '2012-04-10') = (COUNT(PLD.available_date) - 1)
THEN 'Yes'
ELSE 'No'
END) as isAvailable, PL.*
FROM `parking_lot_dates` as PLD
INNER JOIN parking_lots as PL ON PLD.plid = PL.plid
WHERE PLD.available_date BETWEEN '2012-04-01' AND '2012-04-10'
GROUP BY PLD.plid
但是可以将INNER JOIN放入CASE吗?我想要完成的是,当isAvailable列的值为Yes时,抓住额外的信息,否则不要抓住它。
我尝试将INNER JOIN放在CASE语句之间,但它没有用。
提前致谢。
答案 0 :(得分:2)
您不能以您想要的方式进行条件加入,但您可以改为:
SELECT PLD.FROM, PLD.UNTIL, IF(PLD.isAvailable, 'Yes', 'No') AS isAvailable, PL.*
FROM (
SELECT plid
, MIN(available_date) AS `FROM`
, MAX(available_date) AS `UNTIL`
, DATEDIFF('2012-04-01', '2012-04-10') = COUNT(*) - 1 AS `isAvailable`
FROM parking_lot_dates
WHERE available_date BETWEEN '2012-04-01' AND '2012-04-10'
GROUP BY plid
) AS PLD LEFT JOIN parking_lots AS PL ON (
PLD.isAvailable AND PL.plid = PLD.plid
)
WHERE NOT (PLD.isAvailable AND PL.plid IS NULL)
子查询在parking_lot_dates
表上执行分组操作,我们在该表和parking_lots
表之间建立外连接,以便即使连接条件不<时也有记录/ em>满意。了解SQL joins。
WHERE
子句模仿INNER JOIN
的效果,通过消除parking_lots
中预期没有匹配记录的任何结果;如果你实际上不想要这种行为,可以省略它。
答案 1 :(得分:0)
目前还不是很清楚你想要什么。也许你只需要一个HAVING
条款:
SELECT PL.*
FROM parking_lot_dates AS PLD
INNER JOIN parking_lots AS PL
ON PLD.plid = PL.plid
WHERE PLD.available_date BETWEEN '2012-04-01' AND '2012-04-10'
GROUP BY PLD.plid
HAVING DATEDIFF('2012-04-01', '2012-04-10') = COUNT(PLD.available_date) - 1