SELECT
ID
FROM
TABLE111
WHERE COL1 = 33
AND COL2 != 26
AND COL3 = 0
AND COL4 = 1
语句2
SELECT
ID
FROM
TABLE111
WHERE COL1 != 33
AND COL2 = 26
AND COL3 = 0
AND COL4 = 1
我有个覆盖索引
COL1 ,COL2 ,COL3 ,COL4,ID
两条语句都能用到覆盖索引,
单数差距在下面,第一条只扫描了所需要的行
第二条扫描了所有
1 PRIMARY SE_BASE_CONFIG range cover_index cover_index 4 (NULL) 100 Using where; Using index
2 UNION SE_BASE_CONFIG range cover_index cover_index 2 (NULL) 52526 Using where; Using index
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mysql 覆盖索引,不等于条件用不到索引
语句1 SELECT ID FROM TABLE111 WHERE COL1 = 33 AND COL2 != 26 AND COL3 = 0 AND COL4 = 1 语句2 SELECT ID FROM TABLE111 WHERE COL1 != 33 AND COL2 = 26 AND COL3 = 0 AND COL4 = 1 我有个覆盖索引 COL1 ,COL2 ,COL3 ,COL4,ID 两条语句都能用到覆盖索引, 单数差距在下面,第一条只扫描了所需要的行 第二条扫描了所有 1P