联合索引实战

联合索引使用规则 问题：html 假设某个表有一个联合索引（c1,c2,c3,c4）如下只能使用该联合索引的c1,c2,c3部分sql A where c1=x and c2=x and c4>x and c3=xpost B where c1=x and c2=x and c4=x order by c3测试 C where c1=x and c4= x group by c3,c2url D

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