Question

Hello and thank you very much for your time. I am using SQL Server 2008. My challenge is as follows:

I have 3 databases Q_DB, CAN_DB, USA_DB. CAN_DB and USA_DB have the same tables but represent two different countries

The Q_DB has tables of queues. One table is called ACCOUNTS and the columns of interest are ACCOUNTID and SERVER

I want to query the information on the other two databases from the fields of ACCOUNTS. An example is:

Q_DB.dbo.ACCOUNTS

• ID123 CAN_DB
• ID456 USA_DB
• ID789 CAN_DB

I know I can do it this way, but it I was wondering if there is any other approach to obtain the result.

SELECT ACTNAME, AMTDUE, SHIPCOUNTY  
FROM CAN_DB.dbo.Accts 
WHERE ACCTID IN(SELECT ACCOUNTID FROM Q_DB.dbo.ACCOUNTS WHERE SERVER IN('CAN_DB')
UNION ALL
SELECT ACTNAME, AMTDUE, SHIPCOUNTRY 
FROM USA_DB.dbo.Accts
WHERE ACCTID IN(SELECT ACCOUNTID FROM Q_DB.dbo.ACCOUNTS WHERE SERVER IN('USA_DB')

Any help or opinions or suggestions would be greatly appreciated . Thanks

Answer 1

I don’t see why you are using IN with a single value (CAN_DB).

Also, you should precognize EXISTS instead of IN.

SELECT ACTNAME, AMTDUE, SHIPCOUNTRY  
FROM CAN_DB.dbo.Accts a1
WHERE EXISTS (SELECT * FROM Q_DB.dbo.ACCOUNTS WHERE ACCTID = a1.ACCTID AND SERVER = 'CAN_DB')
UNION ALL
SELECT ACTNAME, AMTDUE, SHIPCOUNTRY 
FROM USA_DB.dbo.Accts a2
WHERE EXISTS (SELECT * FROM Q_DB.dbo.ACCOUNTS WHERE ACCTID = a2.ACCTID AND SERVER = 'USA_DB')

Note: Using UNION ALL will return duplicates (if there are some). To have the query select unique rows, use the keyword UNION instead.

EDIT: If you want to sum the AMTDUE from both servers according to same ACTNAME and SHIPCOUNTRY :

SELECT  COALESCE(can.ACTNAME,usa.ACTNAME) as ACTNAME,
        COALESCE(can.AMTDUE,0)+COALESCE(usa.AMTDUE,0) as AMTDUE,
        COALESCE(can.SHIPCOUNTRY,usa.SHIPCOUNTRY) as SHIPCOUNTRY  
FROM    CAN_DB.dbo.Accts can
FULL OUTER JOIN USA_DB.dbo.Accts usa
ON      can.ACTNAME = usa.ACTNAME AND 
        can.SHIPCOUNTRY = usa.SHIPCOUNTRY