Question

I have been reading about the differences between Table Variables and Temp Tables and stumbled upon the following issue with the Table Variable. I did not see this issue mentioned in the articles I pursued.

I pass in a series of PKs via a XML data type and successfully create the records in both temp table structures. When I attempt to update further fields in the temp tables the Table Variable fails but the Temp Table has no problem with the Update Statement. What do need to do different? I would like to take advantage of the speed boost that Table Variables promise…

Here are the SP snippets and Results:

CREATE PROCEDURE ExpenseReport_AssignApprover (     @ExpenseReportIDs       XML ) AS   DECLARE     @ERTableVariable        TABLE   (   ExpenseReportID             INT,                                                 ExpenseReportProjectID      INT,                                                 ApproverID                  INT)   CREATE TABLE #ERTempTable (     ExpenseReportID             INT,     ExpenseReportProjectID      INT,     ApproverID                  INT )  INSERT INTO @ERTableVariable (ExpenseReportID) SELECT ParamValues.ID.value('.','VARCHAR(20)') FROM @ExpenseReportIDs.nodes('/Root/ExpenseReportID') as ParamValues(ID)  INSERT INTO #ERTempTable (ExpenseReportID) SELECT ParamValues.ID.value('.','VARCHAR(20)') FROM @ExpenseReportIDs.nodes('/Root/ExpenseReportID') as ParamValues(ID)  UPDATE          #ERTempTable SET             ExpenseReportProjectID = (  SELECT TOP 1 ExpenseReportProjectID                                                  FROM ExpenseReportItem                                                  WHERE(ExpenseReportID = #ERTempTable.ExpenseReportID))  UPDATE          @ERTableVariable SET             ExpenseReportProjectID = (  SELECT TOP 1 ExpenseReportProjectID                                                  FROM ExpenseReportItem                                                  WHERE(ExpenseReportID = @ERTableVariable.ExpenseReportID)) 

Error when last update statement in there : Must declare the scalar variable ‘@ERTableVariable’.

ExpenseReportProjectID is updated in #ERTempTable when the last update is commented out:

Answer 1

A quick test works when I literalize the table var reference in the last update:

UPDATE @ERTableVariable     SET ExpenseReportProjectID = (               SELECT TOP 1 ExpenseReportProjectID         FROM ExpenseReportItem          WHERE ExpenseReportID = [@ERTableVariable].ExpenseReportID     ) 

You could also use an ‘update from’:

UPDATE er SET      ExpenseReportProjectID = ExpenseReportItem.ExpenseReportProjectID FROM @ERTableVariable er INNER JOIN ExpenseReportItem ON      ExpenseReportItem.ExpenseReportID = er.ExpenseReportID 

The join might return multiple rows but only one will ‘stick’. Kind of a non-deterministic update like ‘TOP 1’.