SQL Server loop through dynamic query

Question

I have a procedure where I pass temporary table name as parameter. For each dataset inside I need to get rowcount. How to achieve this?

I need something like:

CREATE PROCEDURE sp_processing 
  @temp_table_name varchar(50)
AS
  DECLARE @log varchar(max)

/* get list of keys inside temp_table_name */
/* just a pseudo-code example */
SET @l_cursor = CURSOR FOR 
SELECT Key1, Key2, Key3, count(*) 
  FROM @temp_table_name -- table name passed as text 
 GROUP by Key1, Key2, Key3;

WHILE "there are results"
BEGIN
  @log += @Key1 +', '+ @Key2 +', '+ @Key3 +', '+ @count + CHAR(13)+CHAR(10);
END

UPDATE log_table SET log_column = @log WHERE....;

END /* procedure */

Is there a way to loop this?

I know I have option to fetch results to a table type and THEN loop, but that requires to use a table type, so wondering if this is achievable without a table variable.

EDIT: I need just need to print count for each set of keys.

I don't quite understand what you are trying to do. If you recieve the temporary table name as parameter, then you *will* have to access it through dynamic SQL. Why do you need a cursor for it? Why do you need a loop? — EzLo, May 10 '18 at 09:00
Actually you're right, I don't need a loop because I just need to print the counts in a `varchar` variable, but I guess I need to loop through the records :-( — Jakub P, May 10 '18 at 09:46
Include your complete use case in the question so we can avoid the Q&A ping pong. — EzLo, May 10 '18 at 09:49
I found this solution quite neat: https://stackoverflow.com/questions/8005846/sql-server-combining-multiple-rows-into-one-row — Jakub P, May 10 '18 at 10:15

Jakub P · Accepted Answer · 2018-05-10T10:44:11.793

This worked for me:

DECLARE @l_sql nvarchar(max)
DECLARE @temp_table_name varchar(50) = 'SOME_TABLE'
DECLARE @combinedString varchar(max)
SET @l_sql = 'SELECT @combinedString = COALESCE(@combinedString, '''') + convert(varchar,[Key1]) +'', ''+ convert(varchar,[Key3]) +'': ''+ convert(varchar,COUNT(*)) + ''| '' + CHAR(13)+CHAR(10) '
           + '  FROM ' + @temp_table_name  
           + ' GROUP BY [Key1], [Key3]'
           + ' ORDER BY [Key1], [Key3]';

EXECUTE sp_executesql @l_sql, N'@combinedString varchar(max) OUTPUT', @combinedString = @combinedString OUTPUT ;

SELECT @combinedString

Result:

1, 1: 4| 
1, 2: 2| 
1, 3: 1| 
2, 5: 1|

score 1 · Answer 2 · answered May 10 '18 at 10:10

You should always try to avoid looping and cursor. This is a set based solution for your case. Please review (specially the update filter) and see if it suits your needs.

CREATE PROCEDURE sp_processing 
  @temp_table_name varchar(50)
AS
BEGIN

    DECLARE @DynamicSQL VARCHAR(MAX) = '

        ;WITH LogRecords AS
        (
            SELECT
                LogRecord = 
                    ISNULL(T.Key1, '''') + '','' + 
                    ISNULL(T.Key2, '''') + '','' +  
                    ISNULL(T.Key2, '''') + '','' + 
                    CONVERT(VARCHAR(20), COUNT(1))
            FROM
                QUOTENAME(''' + @temp_table_name + ''') AS T
            GROUP BY
                T.Key1,
                T.Key2,
                T.Key3
        )
        UPDATE L SET
            log_column = STUFF(
                (
                    SELECT
                        R.LogRecord + CHAR(13) + CHAR(10)
                    FROM
                        LogRecords AS R
                    FOR XML
                        PATH('')
                ),
                1, 1, '')
        FROM
            log_table AS L
        WHERE
            L.IdFilter = 999999999'

    PRINT @DynamicSQL

    -- EXEC (@DynamicSQL)

END

Thanks for effort. What do You think of this answer, which I find very neat: https://stackoverflow.com/questions/8005846/sql-server-combining-multiple-rows-into-one-row — Jakub P, May 10 '18 at 10:15
The first answer has 2 solutions. The first one only works when filtering a particular set (won't work with group by), the 2nd one is similar to the one I wrote here. However, you can't escape using Dynamic SQL as long as you recieve the table name by parameter. — EzLo, May 10 '18 at 10:19

SQL Server loop through dynamic query

2 Answers2