一个table 3个相同的类型的field分别为a,b,c 下面三个语句哪个执行效率高,速度快
1.select * from table where a = .. and c = ..;
2.select * from table where b= .. and c = ..;
3.select * from table where a = .. and b =.. and c = ..;sqlmysql
1.select * from table where a = .. and c = ..;
2.select * from table where b= .. and c = ..;
3.select * from table where a = .. and b =.. and c = ..;sqlmysql
总不能为追求效率,而无视需求吧?
把*换成 需求的字段吧 会快那么点点