1、select distinct name from tb 2、select distinct name ,subnum from tb 3、解析后都一样 4、group by 后面的字段先后是按照优先级的(distinct 同)group by A,B 即先按照A进行分组,A相同的,按B分组group by B,A 即先按照B进行分组,B相同的,按A分组
select distinct [name] from subject select [name] from subject group by [name]select distinct [name],subnum from subject select [name],subnum from subject group by [name],subnum哪个效率高请打开查询分析器后按Ctl+L执行,看实际情况group by后面的多个列名可以放在where后面进行筛选
2、select distinct name ,subnum from tb
3、解析后都一样
4、group by 后面的字段先后是按照优先级的(distinct 同)group by A,B 即先按照A进行分组,A相同的,按B分组group by B,A 即先按照B进行分组,B相同的,按A分组
select [name] from subject group by [name]select distinct [name],subnum from subject
select [name],subnum from subject group by [name],subnum哪个效率高请打开查询分析器后按Ctl+L执行,看实际情况group by后面的多个列名可以放在where后面进行筛选