ROLLUP Function; Replace NULL with 'Total' w/ Column data type INT not VARCHAR

问题

I'm having some problems replacing my ROLLUP NULL with a string value because my column data type is an Integer.

SELECT CASE
WHEN GROUPING(Column1) = 1 THEN 'Total'
ELSE Column1
END  Column1, SUM(Column2) AS MySum
FROM MyTable
GROUP BY Column1 WITH ROLLUP;

I can put a numeric value in:

WHEN GROUPING(Column1) = 1 THEN '9999'

but I can't figure out how to convert to varchar if value is NULL and then replace with 'Total'.

回答1:

Test Data

DECLARE @MyTable TABLE (Column1 INT,Column2 INT)
INSERT INTO @MyTable VALUES
(1,1),(1,2),(1,3),(2,1),(2,2),(2,3),(3,1),(3,2),(3,3)

SELECT CASE
         WHEN GROUPING(Column1) = 1 THEN 'Total'
         ELSE CAST(Column1 AS VARCHAR(10))     --<-- Cast as Varchar
       END  Column1
      , SUM(Column2) AS MySum
FROM @MyTable
GROUP BY Column1 
WITH ROLLUP;

Result Set

╔═════════╦═══════╗
║ Column1 ║ MySum ║
╠═════════╬═══════╣
║ 1       ║     6 ║
║ 2       ║     6 ║
║ 3       ║     6 ║
║ Total   ║    18 ║
╚═════════╩═══════╝

Note

The reason you couldnt do what you were trying to do is because when you use a CASE statement in each case the returned datatype should be the same.

In above query I have just CAST the colum1 to varchar and it worked.

来源：https://stackoverflow.com/questions/21740326/rollup-function-replace-null-with-total-w-column-data-type-int-not-varchar