、列Cid和列Sid建一个联合索引
create unique index uni_Gid_Cid_SId on student(Gid,Cid,SId)
联合索引 uni_Gid_Cid_SId 实际建立了...(Gid)、(Gid,Cid)、(Gid,Cid,SId)三个索引。...建一个联合索引(Gid,Cid,SId),实际相当于建了(Gid)、(Gid,Cid)、(Gid,Cid,SId)三个索引。每多一个索引,都会增加写操作的开销和磁盘空间的开销。...对联合索引(Gid,Cid,SId),如果有如下的sql: select Gid,Cid,SId from student where Gid=1 and Cid=2。...引申
对于联合索引(Gid,Cid,SId),查询语句SELECT * FROM student WHERE Cid = 465176354 ;是否能够触发索引?