我有点羞于问这个问题,因为我已经使用MySQL多年了,但是哦,好吧.
我有一张表,有两个字段,a
和b
.我将对其运行以下查询:
-
SELECT * FROM ... WHERE A = 1;
个 SELECT * FROM ... WHERE B = 1;
SELECT * FROM ... WHERE A = 1 AND B = 1;
从性能的Angular 来看,is at least one of the following configurations of indexes slower for at least one query?如果是,请详细说明.
-
ALTER TABLE ... ADD INDEX (a); ALTER TABLE ... ADD INDEX (b);
个 -
ALTER TABLE ... ADD INDEX (a, b);
个 ALTER TABLE ... ADD INDEX (a); ALTER TABLE ... ADD INDEX (b); ALTER TABLE ... ADD INDEX (a, b);
谢谢(请注意,我们谈论的是非唯一索引)