【发布时间】：2016-05-10 08:34:29
【问题描述】：
我的这个查询有多个运行很慢的子查询。
SELECT DISTINCT pav.products_options_values_id,
pav.products_options_values_name,
pav.products_options_values_sort_order
FROM products_stock ps,
products_options_values pav,
(
SELECT DISTINCT pa.products_id,
pov.products_options_values_id,
pov.products_options_values_name,
pa.options_values_price,
pa.price_prefix
FROM products_attributes pa,
products_options_values pov,
(
SELECT DISTINCT p.products_image,
p.products_quantity,
p.products_status,
m.manufacturers_id,
p.products_id,
p.products_date_added,
p.products_subimage1,
pd.products_name,
p.products_price,
p.products_length,
p.products_width,
p.products_height,
p.products_tax_class_id,IF(s.status, s.specials_new_products_price, NULL) AS specials_new_products_price,
IF(s.status, s.specials_new_products_price, p.products_price) AS final_price,
IF(p.clearance_price < p.products_cost*2.25, p.clearance_price, p.products_cost*2.25) AS sorting_price
FROM products p
LEFT JOIN manufacturers m
using (manufacturers_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 po
ON pa.options_id = po.products_options_id
LEFT JOIN products_options_values pov
ON pa.options_values_id = pov.products_options_values_id ,
products_description pd,
categories c,
products_to_categories p2c
WHERE p.products_status = '1'
AND p.products_id = pd.products_id
AND pd.language_id = '1'
AND p.products_id = p2c.products_id
AND p2c.categories_id = c.categories_id
AND ((
pd.products_name LIKE '%a%'
OR po.products_options_name LIKE '%a%'
OR pov.products_options_values_name LIKE '%a%'
OR pd.products_description LIKE '%a%') )
ORDER BY p.products_id DESC) m
WHERE m.products_id = pa.products_id
AND pa.options_id = 1
AND pa.options_values_id = pov.products_options_values_id
AND pov.language_id = '1'
GROUP BY pov.products_options_values_id
ORDER BY pov.products_options_values_sort_order ASC) q
WHERE q.products_id = ps.products_id
AND ps.products_stock_attributes = concat('1-', pav.products_options_values_id)
AND ps.products_stock_quantity > 0
ORDER BY pav.products_options_values_sort_order ASC
尝试优化它几个小时，但我可能误读了 EXPLAIN 信息，因为无论我做什么，它似乎都无法让它更快，所以我在这里向专家寻求帮助。
它变得如此缓慢的原因是什么，我应该怎么做才能让它变快？
【问题讨论】：
-
请注意，那里有 4 个条目表明查询正在执行全表扫描，因为索引不可用。在解释的第 1、2、4 和 7 行确保相关列（来自 where 子句）被正确索引。即，如果它是覆盖索引，则列在索引中的排序正确。
标签： mysql performance