1.
select count(distinct CName) from Course
2.
select count(CName) from (select distinct CName from Course) as temp
as可有可无。temp作为别名,若无则提示错误:1248 - Every derived table must have its own alias
mb61bc2ba16eece 博主文章分类:MySQL
1.
select count(distinct CName) from Course
2.
select count(CName) from (select distinct CName from Course) as temp
as可有可无。temp作为别名,若无则提示错误:1248 - Every derived table must have its own alias
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