Question

我有一个优化问题，我想首先执行子查询

EXPLAIN 
SELECT * 
  FROM `References_galaxia`
     , Link_galaxia 
 WHERE linkReferenced IN ( SELECT id 
                             FROM Link_galaxia 
                            WHERE idConceptStart IN (616269,616268,615721) 
                              AND idConceptLink = 315 
                              AND idConceptTarget = 29209 
                         ) 
   AND `References_galaxia`.linkReferenced = Link_galaxia.id 
   AND `References_galaxia`.idConcept IN (416,36053,36088,36037)

主查询将大约一百万条记录的数据量返回到内存中。而子查询

SELECT id FROM Link_galaxia WHERE idConceptStart IN （616269,616268,615721）AND idConceptLink = 315 AND idConceptTarget = 29209）

返回少量数据。如何管理首先执行子查询？

解释的结果

1   PRIMARY References_galaxia  ALL unique_ref,linkReferenced   NULL    NULL    NULL    9163156 Using where
1   PRIMARY Link_galaxia    eq_ref  PRIMARY PRIMARY 4   eds_sandra.References_galaxia.linkReferenced    1   
2   DEPENDENT SUBQUERY  Link_galaxia    eq_ref  PRIMARY,idx_name,idConceptStart,idConceptStart_4,idConceptTarget,idConceptLink  PRIMARY 4   References_galaxia.linkReferenced   1   Using where

非常感谢你的帮助！

Answer 1

SELECT * 
  FROM `References_galaxia`
     , Link_galaxia 
 WHERE `References_galaxia`.linkReferenced = Link_galaxia.id 
   AND `References_galaxia`.idConcept IN (416,36053,36088,36037)
   AND Link_galaxia.idConceptStart IN (616269,616268,615721) 
   AND Link_galaxia.idConceptLink = 315 
   AND Link_galaxia.idConceptTarget = 29209

Answer 2

如下所示的查询似乎更为理想：

SELECT columns, I, actually, want
  FROM `References_galaxia` r
  JOIN Link_galaxia x
    ON x.id = r.linkreferenced
  JOIN Link_galaxia y
    ON y.id = r.linkReferenced 
 WHERE r.idConcept IN (416,36053,36088,36037)
   AND y.idConceptStart IN (616269,616268,615721) 
   AND y.idConceptLink = 315 
   AND y.idConceptTarget = 29209

有关提高此查询性能的帮助，我们需要查看所有相关表的表创建语句，以及EXPLAIN。

Answer 3

只需在变量

中运行修改后的子查询和商店ID

SELECT id INTO @idvar FROM Link_galaxia 
                     WHERE idConceptStart IN (616269,616268,615721) 
                     AND idConceptLink = 315 
                     AND idConceptTarget = 29209

将此var（@idvar）包含在主SQL

中

SELECT * 
  FROM `References_galaxia`
     , Link_galaxia 
 WHERE linkReferenced IN @idvar 
  AND `References_galaxia`.linkReferenced = Link_galaxia.id 
  AND `References_galaxia`.idConcept IN (416,36053,36088,36037);

完整代码可以与事务：

START TRANSACTION;
SELECT id INTO @idvar FROM Link_galaxia 
                         WHERE idConceptStart IN (616269,616268,615721) 
                         AND idConceptLink = 315 
                         AND idConceptTarget = 29209;
SELECT * 
  FROM `References_galaxia`
     , Link_galaxia 
 WHERE linkReferenced IN @idvar 
  AND `References_galaxia`.linkReferenced = Link_galaxia.id 
  AND `References_galaxia`.idConcept IN (416,36053,36088,36037);
COMMIT;

SQL子查询优化，如何先执行子查询

3 个答案: