对于这种情况需要一个sql查询

Question

大家好，请帮助我为该情况连接一个SQL查询

表

+----+---------+--------+------------+--------------+
| ID | country | region | restaurant | locationcode |
+----+---------+--------+------------+--------------+
|  1 | IND     | DL     | xyz        |          100 |
|  2 | IND     | DL     | yzc        |          111 |
+----+---------+--------+------------+--------------+

选择所有项目-

if condition matched with country,region,restaurant,locationcode
  If not then all items that matched condition with country,region,restaurant
      if not then all items that matched the condition with country,region

我可以使用sql查询还是必须使用应用程序逻辑来处理？

Answer 1

这个解决方案有点冗长，但应该可以。 使用CASE从选项中进行选择，然后使用这些行的存在作为选择条件。

SELECT id FROM mytable WHERE 
CASE 
     WHEN EXISTS( SELECT 1 FROM mytable WHERE region='DL' AND country='IND'
                   AND restaurant='xyz' AND locationcode='100')
       THEN region='DL' AND country='IND' AND restaurant='xyz' AND locationcode='100'
     WHEN EXISTS( SELECT 1 FROM mytable WHERE region='DL' AND country='IND')
       THEN region='DL' AND country='IND'
     WHEN EXISTS( SELECT 1 FROM mytable WHERE region='DL' )
       THEN region = 'DL';
     END; 

Answer 2

可以使用IF这样实现

SELECT 
    * 
FROM mytable mt
WHERE
    IF(
        mt.region='DL' 
        AND mt.country='IND' 
        AND mt.restaurant='xyz' 
        AND mt.locationcode='100',
        1,
        IF(
            mt.region='DL' 
            AND mt.country='IND' 
            AND mt.restaurant='xyz',
            1,
            IF(
                mt.region='DL' 
                AND mt.country='IND'
            ,1,
            'Nothing Found')
        )
    )

Answer 3

我认为，如果我们想用SQL做，那么更好的方法是用SQL块做。

类似于此处给出的示例： https : //stackoverflow.com/a/11222053/555953