Question

Hi there i have a table:

Teams: as below

|Team ID  | Member ID|
| 1       |  10       |
| 2       |  230      |
| 1       |  11       |
| 4       |  56       |
| 1       |  15       |
| 2       |  236      |
| 1       |  18       |
| 3       |  43       |
| 1       |  17       |

I did this to find the members of a team:

SELECT members from teams where team_ID = 1; and it gave me 10,11,15,18,17

I have a different table for each member .So I tried something like this to fetch the data from different tables and it worked fine:

SELECT * FROM 10
UNION ALL 
SELECT * FROM 11
UNION ALL 
SELECT * FROM 15
UNION ALL 
SELECT * FROM 18
UNION ALL 
SELECT * FROM 17

Is it possible to make this 2 Queries into 1 Query because the members of a team changes dynamically….

Any help please…

Let me be bit more clear: My final result should only contains data from different member tables. Hope I am clear..

Answer 1

First, I strongly advise that you consider a redesign of your table structure otherwise you will have a difficult time querying this data.

You can do something like this though. Of course, this only works if you know the tables member tables that you want to query:

select *
from teams t
left join
(
  SELECT *, 10 Member 
  FROM 10
  UNION ALL 
  SELECT * , 11 Member 
  FROM 11
  UNION ALL 
  SELECT * , 15 Member 
  FROM 15
  UNION ALL 
  SELECT * , 18 Member 
  FROM 18
  UNION ALL 
  SELECT * , 17 Member 
  FROM 17
) m
  on t.memberid = m.member

If you want to do this dynamically, then you might be able to use a prepared statement similar to this:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'select *, ',
      MemberID,
      ' AS Member from ', MemberID, '
       '
    )
  separator ' union all ') 
  INTO @sql
FROM teams
WHERE TeamID = 1;

SET @sql = CONCAT('select *
                   from teams t 
                   left join
                   (', @sql, ' ) m
                     on t.memberid = m.member');

-- select @sql

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;