FROM `product_option_value` where option_value_id =3) p1, (
SELECT *
FROM `product_option_value` where option_value_id =4
)p2, (
SELECT *
FROM `product_option_value` where option_value_id =5
)p3
WHERE p1.product_id = p2.product_id
AND p1.product_id = p3.product_id
为什么p1,p2,p3都用不了索引的?
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 876
1 PRIMARY <derived4> ALL NULL NULL NULL NULL 1093 Using where
1 PRIMARY <derived3> ALL NULL NULL NULL NULL 1153 Using where
4 DERIVED product_option_value ref option_value_id option_value_id 4 1093
3 DERIVED product_option_value ref option_value_id option_value_id 4 1152
2 DERIVED product_option_value ref option_value_id option_value_id 4 876
id 1三个都用不到索引..
