Question

I have the following tables:

T1

  ID  PRIORITY
  1      1
  2      1
  3      2
  4      4

T2

ID  SERVICE
1   PSTN
1   ADSL
3   ADSL

T3

ID   DEVICE
1    BSC1
3    BSC7 
4    BSC7

I want as output

ID  PRIORITY SERVICE/DEVICE
1      1        PSTN
1      1        ADSL
1      1        BSC1
2      1
3      2        ADSL
3      2        BSC7

How to bind those tables using UNION ALL? Also I must put WHERE clause for T1 WHERE PRIORITY!=4

Total number in output table for one id should be the summary of T2+T3 (FOR ID=1 2+1=3) but for ID=2 it also SHOULD exist in table output with blank second column.

Thank you

Answer 1

If you are okay using just a UNION and not UNION ALL this should give you what you want

SELECT t1.Id, t1.Priority, COALESCE(t2.Service, '') AS [Service/Device]
FROM t1
LEFT JOIN t2 ON t1.Id = t2.Id
WHERE t1.Priority != 4

UNION 

SELECT t1.Id, t1.Priority, COALESCE(t3.Device, '') AS [Service/Device]
FROM t1
LEFT JOIN t3 ON t1.Id = t3.Id
WHERE t1.Priority != 4

SQL Fiddle example