SQL Server Dynamic SQL - Get output from list of tables - sql

Question

I am trying to loop through a temp table variable that contains a list of table names. I want to simply count the rows in each table where a DateTracked column is greater than 30 days. I am having trouble dynamically changing the FROM #tblName variable to store the record count and then insert it into my tracking table. Eventually I will use a cursor to loop through each, but I just want to get this logic down first for a single table. Here is my test code:
DECLARE #tblName as NVARCHAR(MAX)
DECLARE #q as NVARCHAR(MAX)
SET #q = 'Select Count(DateTracked) FROM Audit.' + #tblName + ' WHERE DateTracked > DATEADD(dd, -30, CAST(GETDATE() as date))'
--DECLARE #tblNameTable TABLE
--(
-- tableName NVARCHAR(MAX)
--)
--INSERT INTO #tblNameTable VALUES (N'myTestTable')
DECLARE #ExpectedRecordsToMove AS TABLE (col1 int)
INSERT INTO #ExpectedRecordsToMove EXECUTE sp_executesql #q, N'#tblName nvarchar(500)', #tblName = 'myTestTable'
SELECT * FROM #ExpectedRecordsToMove

Answer 1

Found solution.
DECLARE #tblName as NVARCHAR(MAX) = 'tblAutoDispatch_DispatchStatus_Map_Tracking'
DECLARE #q as NVARCHAR(MAX) = 'SELECT Count(DateTracked) FROM Audit.' + #tblName + ' WHERE DateTracked > DATEADD(dd, -30, CAST(GETDATE() as date))'
DECLARE #ExpectedRecordsToMove TABLE
(
ExpectedRecordsToMove Int
)
INSERT INTO #ExpectedRecordsToMove
EXECUTE sp_executesql #q
SELECT * FROM #ExpectedRecordsToMove
Note: Answer provided by OP on question.

Answer 2

sp_executesql also allows for output parameters. It is possible to assign variable inside the inner query and return the value.
DECLARE #tblName AS NVARCHAR(MAX) = N'tblAutoDispatch_DispatchStatus_Map_Tracking';
DECLARE #q AS NVARCHAR(MAX)
= N'SELECT #rowcount = COUNT(DateTracked) FROM Audit.' + #tblName
+ N' WHERE DateTracked > DATEADD(dd, -30, CAST(GETDATE() as date))';
DECLARE #rowcount INT;
EXECUTE sp_executesql
#query = #q,
#parameters = N'#rowcount INT OUTPUT',
#rowcount = #rowcount OUTPUT;
SELECT
#rowcount;

Answer 3

You can actually do this without a cursor, by building up the query in one go
You must use QUOTENAME to ensure table names do not cause syntax errors
You cannot parameterize a table name, it must be inserted directly into dynamic SQL
DECLARE #tablenames TABLE (schemaName sysname, tblName sysname);
-- insert schema and table names
DECLARE #sql nvarchar(max) = N'
SELECT
ISNULL(tblName, ''Grand Total'') AS tblName,
SUM(rowcount) AS rowcount
FROM (
' +
(
SELECT STRING_AGG(CAST(
N' SELECT ' + QUOTENAME(tn.schemaName, '''') + N'.' + QUOTENAME(tn.tblName, '''') + N' AS tblName,
Count(DateTracked) AS rowCount
FROM ' + QUOTENAME(tn.schemaName) + N'.' + QUOTENAME(tn.tblName) + N'
WHERE DateTracked > DATEADD(dd, -30, CAST(GETDATE() as date))'
AS nvarchar(max)), N'
UNION ALL
')
FROM #tablenames tn
JOIN sys.tables t ON tn.schemaName = SCHEMA_NAME(t.schema_id) AND tn.tblName = t.name
) + N'
) AS tables
GROUP BY ROLLUP(tblName);
';
PRINT #sql; -- for testing
EXEC (#sql);
If you don't have STRING_AGG on your version of SQL Server, you must use FOR XML instead