Question

I have a table, 6 columns, the 6th column is empty but the other 5 have data. I used the 4th and 5th columns to calculate a value and then I wish to insert this value into the 6th column.

This is what I have so far:

UPDATE Table_Name 
SET Change = tab3.Difference
FROM
    (SELECT COBDate, FileName, ID, ScenarioID FROM Table_Name WHERE COBDate = '2012-05-18' AND FileName = 'GBP.csv') tab0
INNER JOIN
    (SELECT  tab1.ID, tab1.ScenarioID,tab1.COBDate, tab1.FileName, Val1 - Val2 AS Difference FROM
        (SELECT COBDate, FileName, ScenarioID, ID, CASE WHEN Value IS NULL THEN 0 ELSE Value END AS Val1 FROM Table_Name WHERE COBDate = '2012-05-18' AND FileName = 'GBP.csv') tab1
    JOIN
        (SELECT COBDate, FileName, ScenarioID, ID, CASE WHEN Value IS NULL THEN 0 ELSE Value END AS Val2  FROM Table_Name WHERE COBDate = '2012-05-17' AND FileName = 'GBP.csv') tab2
    ON tab1.ScenarioID = tab2.ScenarioID AND tab1.ID = tab2.ID) tab3
ON tab0.COBDate = tab3.COBDate
AND tab0.FileName = tab3.FileName
AND tab0.ID = tab3.ID
AND tab0.ScenarioID = tab3.ScenarioID

EDIT: The above code hasn’t worked. It has set the same value for every single row regardless of the primary key….

Answer 1

Does this solve your problem?

UPDATE Table_Name SET Column6 = Column4 + Column5

To get the right rows, use a WHERE statement.