問(wèn)題描述

表

idlevelsort_num110210320420520630730830930

要求得到

idlevelsort_num111212321422523631732833934

即頁(yè)面的展示順序如下

level1

1

2

level2

1

2

3

level3

1

2

3

4

目前的sql

set @index:=0; update t set sort_num = (@index:=@index+1) where level = 1 order by id;set @index:=0; update t set sort_num = (@index:=@index+1) where level = 2 order by id;set @index:=0; update t set sort_num = (@index:=@index+1) where level = 3 order by id;

不知有沒(méi)更簡(jiǎn)潔的sql可以實(shí)現(xiàn)上述的需求？

補(bǔ)充

在線(xiàn)sql

問(wèn)題解答

回答1：

如果只是為了頁(yè)面展示，不需要更新表的數(shù)據(jù)吧。可以試試下面的sql

select level, @sort_num:=if(@prev_level=t1.level, @sort_num+1, 1)from (select * from t order by id) t1, (SELECT @sort_num:=1, @prev_level:=NULL) varorder by id