MySQL中没有选择数据时如何查看所有数据并替换为字符串

Question

I have problem to view all data when I put the create character represent for all group. I have field group in my table. The field has id 1, 2, 3, 4 and I also have put the case statement. When I put the id 1, then the result will be group1 and so on. What I want is when I put the character 'A' . Then the all data in group will display. How to do that? I have no idea.

This is my code:-

select case when a.group='1' then 'group1'
    when a.group='2' then 'group2'
    when a.group='3' then 'group3'
    when a.group='4' then 'group4'
    when a.group='A' then 'ALL GROUP'
    end as group
from kumpulan a
where (a.group = &GROUP or &GROUP = 'A')

if Group='A' then display 'Group 1','Group 2','Group 3','Group 4' in 4 rows

Answer 1

If problem is in 'group' column you should change a.group by &GROUP as:

select 
  case when &GROUP='1' then 'group1' 
  when &GROUP='2' then 'group2' 
  when &GROUP='3' then 'group3' 
  when &GROUP='A' then 'ALL GROUP' 
  end as group 
from 
 kumpulan a 
where (a.group = &GROUP or &GROUP = 'A')

I supose that this query is an abstrat of your real big query that may be something like:

select 
  case when &GROUP='1' then 'group1' 
  when &GROUP='2' then 'group2' 
  when &GROUP='3' then 'group3' 
  when &GROUP='A' then 'ALL GROUP' 
  end as `group` ,
  sum( some_column ) as total
from 
 kumpulan a 
where (a.group = &GROUP or &GROUP = 'A')
group by `group`

Answer 2

        select case 'A' when a.group='1' then 'group1' when a.group='2' then 'group2' when a.group='3' then 'group3' when a.group='A' then 'ALL GROUP' end as group from kumpulan a where (a.group = &GROUP or &GROUP = 'A');

Example for this:

       SELECT CASE 1 WHEN 1 THEN 'one' WHEN 2 THEN 'two' ELSE 'more' END;
    -> 'one'