我有这个非常慢的查询，它计算具有特定规格的产品，是解决方案索引吗？或其他解决方案？
select count(DISTINCT if(ps10.specification in ('Meisje'),p.products_id,NULL)) as count1 ,count(DISTINCT if(ps10.specification in ('Jongen'),p.products_id,NULL)) as count2 ,count(DISTINCT if(ps10.specification in ('Unisex'),p.products_id,NULL)) as count3 from (products p)
join (products_to_categories p2c)
on (p.products_id = p2c.products_id)
left join (specials s)
on (p.products_id = s.products_id)
left join (products_attributes pa)
on (p.products_id = pa.products_id)
left join (products_options_values pv)
on (pa.options_values_id = pv.products_options_values_id)
left join (products_stock ps)
on (p.products_id=ps.products_id and pv.products_options_values_id = ps.products_options_values_id2)
INNER JOIN products_specifications ps10 ON p.products_id = ps10.products_id INNER JOIN products_specifications ps17 ON p.products_id = ps17.products_id where p.products_status = '1' and ps.products_stock_quantity>0 and p2c.categories_id in (2,54,60,82,109,115,116,118,53,58,104,55,101,75,56,64,66,67,68,69,70,71,84,103,114,80,92,99,93,94,95,97,106) AND ps10.specifications_id = '10'
AND ps10.language_id = '1'
AND ps17.specification in ('Babyslofjes'
) AND ps17.specifications_id = '17'
AND ps17.language_id = '1'
解释这个查询给了我这个结果：
+----+-------------+-------+--------+-------------------------------------+-------------------------------------+---------+------------------------------------------+-------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+--------+-------------------------------------+-------------------------------------+---------+------------------------------------------+-------+--------------------------+
| 1 | SIMPLE | ps | ALL | idx_products_stock_attributes | NULL | NULL | NULL | 16216 | Using where |
| 1 | SIMPLE | p | eq_ref | PRIMARY | PRIMARY | 4 | kikleding.ps.products_id | 1 | Using where |
| 1 | SIMPLE | s | ref | idx_specials_products_id | idx_specials_products_id | 4 | kikleding.p.products_id | 1 | Using index |
| 1 | SIMPLE | p2c | ref | PRIMARY | PRIMARY | 4 | kikleding.ps.products_id | 1 | Using where; Using index |
| 1 | SIMPLE | pv | ref | PRIMARY | PRIMARY | 4 | kikleding.ps.products_options_values_id2 | 1 | Using where; Using index |
| 1 | SIMPLE | ps10 | ref | products_id | products_id | 12 | kikleding.p.products_id,const,const | 1 | Using where |
| 1 | SIMPLE | ps17 | ref | products_id | products_id | 12 | kikleding.ps.products_id,const,const | 1 | Using where |
| 1 | SIMPLE | pa | ref | idx_products_attributes_products_id | idx_products_attributes_products_id | 4 | kikleding.p2c.products_id | 6 | Using where |
+----+-------------+-------+--------+-------------------------------------+-------------------------------------+---------+------------------------------------------+-------+--------------------------+
将左连接更改为内部连接，如下所示：
select count(DISTINCT if(ps10.specification in ('Meisje'),p.products_id,NULL)) as count1 ,count(DISTINCT if(ps10.specification in ('Jongen'),p.products_id,NULL)) as count2 ,count(DISTINCT if(ps10.specification in ('Unisex'),p.products_id,NULL)) as count3 from (products p)
inner join (products_to_categories p2c)
on (p.products_id = p2c.products_id)
left join (specials s)
on (p.products_id = s.products_id)
inner join (products_attributes pa)
on (p.products_id = pa.products_id)
inner join (products_options_values pv)
on (pa.options_values_id = pv.products_options_values_id)
inner join (products_stock ps)
on (p.products_id=ps.products_id and pv.products_options_values_id = ps.products_options_values_id2)
INNER JOIN products_specifications ps10 ON p.products_id = ps10.products_id INNER JOIN products_specifications ps17 ON p.products_id = ps17.products_id where p.products_status = '1' and ps.products_stock_quantity>0 and p2c.categories_id in (2,54,60,82,109,115,116,118,53,58,104,55,101,75,56,64,66,67,68,69,70,71,84,103,114,80,92,99,93,94,95,97,106) AND ps10.specifications_id = '10'
AND ps10.language_id = '1'
AND ps17.specification in ('Babyslofjes'
) AND ps17.specifications_id = '17'
AND ps17.language_id = '1'
我索引了ps.products_id
它快一点，谢谢你的评论，但查询仍然很慢
答案 0 :(得分：0)
显然使用p.products_id更多，所以首先索引表Products中的属性。然后pv.products_options_values_id并尝试索引您在Inner Join中使用的其他属性。还尝试转换在Join条件中使用的条件特别适用于Inner join
答案 1 :(得分：0)
我会稍微修改一下查询，将条件从where部分放入连接中，从样本中我认为你也可以摆脱Specials表。
select
count(distinct if(ps10.specification in ('Meisje'), p.products_id, null)) as count1,
count(distinct if(ps10.specification in ('Jongen'), p.products_id, null)) as count2,
count(distinct if(ps10.specification in ('Unisex'), p.products_id, null)) as count3
from (products p)
inner join (products_to_categories p2c)
on (p.products_id = p2c.products_id)
inner join (products_attributes pa)
on (p.products_id = pa.products_id)
inner join (products_options_values pv)
on (pa.options_values_id = pv.products_options_values_id)
inner join (products_stock ps)
on (p.products_id=ps.products_id and pv.products_options_values_id = ps.products_options_values_id2 and ps.products_stock_quantity > 0)
inner join products_specifications ps10
ON p.products_id = ps10.products_id and ps10.language_id = '1' and ps10.specifications_id = '10'
inner join products_specifications ps17
ON p.products_id = ps17.products_id and ps17.language_id = '1' and ps17.specifications_id = '17'
where p.products_status = '1'
and p2c.categories_id in (2,54,60,82,109,115,116,118,53,58,104,55,101,75,56,64,66,67,68,69,70,71,84,103,114,80,92,99,93,94,95,97,106)
and ps17.specification in ('Babyslofjes')
至于索引，我会检查以下内容：
从表名中我怀疑这是一个OS / XTcommerce数据库，我会尝试在几个小时内拿到一个并提供更详细的意见。我只是不记得products_stock和products_specifications，那些都是表，而不是视图，对吗？