Question

我需要在mysql上创建一个视图，其中查询具有带变量的不同类别名称。变量用于为每个类别生成id。

这是我的sql，任何人都可以帮助我，因为我无法使用这种SQL语法创建视图。

create view cat1_view as (SELECT distinct categorylev1, 
       @rownum := @rownum + 1 AS id
  FROM topic t, 
       (SELECT @rownum := 0) r
group by categorylev1)

Answer 1

这样的东西？

/*
create temporary table t(can_id int,    status varchar(20));

insert into t values            
(001 ,   'section 1 question 1'),    
(001 ,   'section 1 question 2'),   
(001 ,   'section 1 question 3'),  
(001 ,   'section 1 question 4'),    
(001 ,   'section 2 question 1'),    
(001 ,   'section 2 question 2'),    
(001 ,   'section 2 question 3'),    
(001 ,   'section 2 question 4'),    
(001 ,   'section 3 question 1'),    
(001 ,   'section 3 question 2'),    
(001 ,   'section 3 question 3'),    
(002 ,   'section 1 question 1'),
(002 ,   'section 1 question 2'),
(002 ,   'section 1 question 3'),
(002 ,   'section 2 question 1'),
(002 ,   'section 2 question 2'),
(002 ,   'section 2 question 3'),
(002 ,   'section 3 question 1'),
(002 ,   'section 3 question 2'),
(002 ,   'section 3 question 3'),
(002 ,   'section 3 question 4');

*/

select   distinct s.canid from
(
select   t.can_id as tcanid, t.status as tstatus ,
            case when @previd <> substring(t.status,1,9) then
            @sno :=if(@previd <> substring(t.status,1,9),@sno + 1,1) 
            else @sno
            end  as canid
          ,@previd:=substring(t.status,1,9) prevcanid
from t,
(select @sno:= 0) as sn
,(select @Previd:= '') as p
order   by substring(t.status,1,9)
) s

如何在mysql上创建视图，其中select语句具有变量

1 个答案: