UPDATE – FROM … again

I already told about UPDATE statement with FROM clause, here.
Have you already used with real-time generated data in SET clause ?
Something with GETDATE() o NEWID() … like this:

UPDATE Campaigns
SET Campaigns.FieldDate = A.MyDate
FROM Campaigns AS C JOIN 
  ( SELECT GETDATE() as MyDate, ID
    FROM Agents
  ) AS A
  ON C.IDAgent = A.ID;

What happened? 😦

You suppose GETDATE() returns a value same as A2.ID, a unique date paired to agent ID, and that value will not change… WRONG!
It’s a function, and that value will change every time SET clause run. 😦

Please, try with NEWID() and you’ll see. :/
I’ll have a look deeper, something does’nt work as expected.

Technorati tags: SQL Server, SQL, UPDATE


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