MYSQL , MAX( IF( condition ) ) 或子查询条件中的性能

Question

我需要在 table 上搜索额外字段作为列，它适用于 2 个不同的解决方案：

Table：盒子

+ -- + ----- + ---- +
| id | name  | vinc |
|----|-------|------|
| 1  | box1  | 22   |
| 2  | box2  | 45   |
| 3  | box3  | 60   |
+ -- + ----- + ---- +

Table: 提取

+ -- + ---- + ----- + ------- +
| id | vinc | type  | value   |
+----+------+-------+---------+
| 1  | 22   | color | #fafafa |
| 2  | 22   | size  | 100     |
| 3  | 45   | size  | 200     |
+ -- + ---- + ----- + ------- +

需要

+ ---- + ---- + ------- +
| name | size | color   |
+------+------+---------+
| box1 | 100  | #fafafa |
| box2 | 200  |         |
| box3 |      |         |
+ ---- + ---- + ------- +

我用子查询做到了并且工作了，但有时我需要按 extr.value 的值搜索查询，导致更多过程：

SELECT 
    box.name
    ,(select extr.value from ext where extr.name = 'size' and box.vinc = extr.vinc) as size
    ,(select extr.value from ext where extr.name = 'color' and box.vinc = extr.vinc) as color
    ... 1 to X extra fields
from box
(sometimes)
where 
    (select extr.value from ext where extr.name = 'size' and box.vinc = extr.vinc) = 'user_inputed value' 
    and... 1 to X

或

SELECT 
    box.name
    ,MAX( if( extr.name = 'size' , extr.value , '' ) ) as size
    ,MAX( if( extr.name = 'color' , extr.value , '' ) ) as color
FROM box    
LEFT JOIN extr on box.vinc = extr.vinc
WHERE
   if( extr.name = 'size' , extr.value , '' ) = 'user_inputed_value'

两者都按方框分组，所以我没有重复行（我认为）select。

这些查询有自动构造函数，所以我不易于使用或在之后调试时遇到问题。

问题是：哪种最佳做法 and/or 性能最好？ :)

Answer 1

另一种选择是加入 extr 两次。

SELECT b.name, eSize.value AS size, eColor.value AS color
    , ...
FROM box AS b 
LEFT JOIN extr AS eSize ON b.vinc = eSize.vinc AND sSize.name = 'size'
LEFT JOIN extr AS eColor ON b.vinc = eColor.vinc AND eColor.name = 'color'
WHERE ...

MYSQL , MAX( IF( condition ) ) 或子查询条件中的性能

Performance in MYSQL , MAX( IF( condition ) ) or Subquery condition

mysql

performance

entity-attribute-value