check if id exists in multiple tables

Question

I am using SQL Server 2012.

I have 5 tables (lets call them A, B, C, D & E). Each table contains a column called m_id, which contains id\'s that are nvarchar(10).

Answer 1

You can use this:

SELECT CASE WHEN COUNT(*) > 0 THEN 1 ELSE 0 END as returnCode
FROM (
    SELECT m_id, N'A' as tableName FROM A WHERE m_id = 'some_id'
    UNION ALL
    SELECT m_id, N'B' as tableName FROM B WHERE m_id = 'some_id'
    UNION ALL
    SELECT m_id, N'C' as tableName FROM C WHERE m_id = 'some_id'
    UNION ALL
    SELECT m_id, N'D' as tableName FROM D WHERE m_id = 'some_id'
    UNION ALL
    SELECT m_id, N'E' as tableName FROM E WHERE m_id = 'some_id'
) data

Answer 2

You could use UNION(removes duplicates beforehand) or UNION ALL:

SELECT CASE WHEN EXISTS 
  ( SELECT 1 FROM ( SELECT m_id FROM  A 
                    UNION 
                    SELECT m_id FROM  B 
                    UNION 
                    SELECT m_id FROM  C 
                    UNION 
                    SELECT m_id FROM  D 
                    UNION 
                    SELECT m_id FROM  E ) All 
    WHERE  All.m_id = 'some_id') 
THEN 1 ELSE 0 END AS ContainsID