mysql笔记--group by,limit用法

Posted 2020-10-11 孤独风中一匹狼

table:
id tag status
1   a     0
2   b      0
3    c     1
4    d    1


一、group by用法
    1.与count 联合计数
           select status,count(*)
          from table
           group by status

status  count(*)
0          2
1           2

    2.与 group_concat联合使用
        select status,group_concat(tag) as tag
        from table
        group by status  
status    tag
0          a,b
1          c,d

二、limit用法
    1.分页
        设页数为page ,每页记录为a

      select *
      from table    
      limit (page-1)*a

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