Mysql 将查询简化为案例

以下是到目前为止的查询：

select `formeid`, `name`, 'm' as `gender` from `data_pokemon`
    where `genders` not like '0|_' and `formeid` not in
        (select `formeid` from `dex` where `userid`=@userid and `gender`='m')
union
select `formeid`, `name`, 'f' as `gender` from `data_pokemon`
    where `genders` not like '_|0' and `formeid` not in
        (select `formeid` from `dex` where `userid`=@userid and `gender`='f')
union
select `formeid`, `name`, 'n' as `gender` from `data_pokemon`
    where `genders`='0|0' and `formeid` not in
        (select `formeid` from `dex` where `userid`=@userid and `gender`='n')
order by `formeid`

---

正如你所看到的，有很多重复。有没有办法简化这个查询，这样就不会有太多事情发生？

我明白了。这在索引使用方面有多高效？@Kolink:

p.genders不像“\u124; 0”

是唯一一个不能使用索引的位，但它也存在于原始查询中；根据您的数据结构，您可能能够对其进行改进（例如，将

'f'

性别作为

CASE

表达式的

ELSE

子句），否则您必须将该列标准化。除此之外，

data\u pokemon.（genders，formeid）

和

dex.（userid，gender，formeid）

上的索引应该被证明非常有效。

SELECT   p.formeid, p.name,
         CASE
           WHEN p.genders NOT LIKE '0|_' THEN 'm'
           WHEN p.genders NOT LIKE '_|0' THEN 'f'
           WHEN p.genders =        '0|0' THEN 'n'
         END AS gender
FROM     data_pokemon p LEFT JOIN dex d
      ON p.formeid = d.formeid
     AND d.userid  = @userid
     AND d.gender  = CASE
           WHEN p.genders NOT LIKE '0|_' THEN 'm'
           WHEN p.genders NOT LIKE '_|0' THEN 'f'
           WHEN p.genders =        '0|0' THEN 'n'
         END
WHERE    d.formeid IS NULL
ORDER BY p.formeid