Question

好的，我要再试一次......这次我肯定是对的。对此感到抱歉。：（

表1 ：

+----+---------+------------+------+
| id | item_id | product_id | type |
+----+---------+------------+------+

table2，table3，table4 ：

+----+---------+
| id | item_id |
+----+---------+

这是我的主要查询：

$sql = "SELECT t1.* FROM table1 AS t1, table2 AS t2 WHERE t2.id = '1' AND 
t2.item_id = t1.item_id AND t1.type NOT IN ('type1', 'type2') LIMIT 5";

$a = mysql_query($sql);
while($b = mysql_fetch_assoc($a))

现在我想整合这两个查询：

第一次查询：

AND IF t1.type = 'type3'然后

SELECT t3.item_id FROM table3 AS t3 WHERE t3.id = t1.product_id AND
t3.item_id NOT IN (SELECT t2.item_id FROM table2 AS t2 WHERE t2.id = '1')

仅当上述查询中的此语句t3.item_id NOT IN (...)为真时，才会显示主查询中的t1.id。但是，如果t3.item_id is IN (...)，则应将其从结果中排除。

第二次查询：

AND IF t1.type = 'type4'然后

SELECT t4.item_id FROM table4 AS t4 WHERE t4.id = t1.product_id AND
t4.item_id NOT IN (SELECT t2.item_id FROM table2 AS t2 WHERE t2.id = '1')

与第一次查询相同。

这一切都适合一个查询吗？我只在一个查询中需要它，所以我知道在下一页显示哪些结果，例如LIMIT 5,5

Answer 1

在mysql中应用flow control flow structure

CASE case_value
    WHEN when_value THEN statement_list
    [WHEN when_value THEN statement_list] ...
    [ELSE statement_list]
END CASE

或者：

CASE
    WHEN search_condition THEN statement_list
    [WHEN search_condition THEN statement_list] ...
    [ELSE statement_list]
END CASE

Answer 2

我不确定我是否理解正确，但我认为应该使用(NOT) EXISTS：

SELECT t1.* 
FROM table1 AS t1
  JOIN table2 AS t2 
    ON t2.item_id = t1.item_id
WHERE t2.id = '1' 
  AND t1.type NOT IN ('type1', 'type2')
  AND NOT ( t1.type = 'type3' 
            AND EXISTS 
                ( SELECT t3.item_id
                  FROM table3 AS t3
                  WHERE t3.id = t1.product_id
                    AND t3.item_id NOT IN
                          ( SELECT t2.item_id 
                            FROM table2 AS t2
                            WHERE t2.id = '1' )
                )
           ) 
  AND NOT ( t1.type = 'type4' 
            AND EXISTS 
                ( SELECT t4.item_id
                  FROM table4 AS t4
                  WHERE t4.id = t1.product_id
                    AND t4.item_id NOT IN
                          ( SELECT t2.item_id 
                            FROM table2 AS t2
                            WHERE t2.id = '1' )
                )
           ) 
ORDER BY WhatYouWant
LIMIT x,y

我如何将这些查询合并为一个？

2 个答案: