第一种方法:
select (@i:=@i+1) as i,table_name.* from table_name,(select @i:=0) as it
第二种方法:
set @rownum=0;
select @rownum:=@rownum+1 as rownum, t.username from auth_user t limit 1,5;
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mysql小知识补充:
创建复合索引
创建联合索引的语法:create index 索引名 on 表名(字段名1,字段名2)
给username和password创建联合索引:create index t1_username_password on t1(username,password)