mysql聯合索引的使用規則

從一道有趣的題目開始分析：spa 假設某個表有一個聯合索引（c1,c2,c3,c4）如下選項哪些字段使用了該索引： A where c1=x and c2=x and c4>x and c3=x B where c1=x and c2=x and c4=x order by c3 C where c1=x and c4= x group by c3,c2 D where c1=? and c5=?

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