Dynamic Database in SubQuery - sql

Question

SELECT
email, password,GP_employee_id, company,
(select distinct CHEKNMBR from [BSL].[dbo].[UPR30300] WHERE EMPLOYID = GP_employee_id and CHEKDATE > GETDATE() - 20 ) as slip_number,
(select distinct CONVERT(date , CHEKDATE) from [BSL].[dbo].[UPR30300] WHERE EMPLOYID = GP_employee_id and CHEKDATE > GETDATE() - 20 ) as slip_number
FROM [payslips].[dbo].[myapp_user]
I would like [BSL] to be dynamic. The value would depend on the company field of the main query. So I want something like this [company].[dbo].[UPR30300]

Answer 1

You can do one big dynamic UNION ALL query
DECLARE #unioned nvarchar(max) = (
SELECT STRING_AGG(CAST(
'
SELECT *, company = ' + QUOTENAME(company, '''') + '
FROM ' + QUOTENAME(company) + '.[dbo].[UPR30300]
WHERE CHEKDATE > DATEADD(day, -20, GETDATE())
'
AS nvarchar(max)), 'UNION ALL')
FROM (
SELECT DISTINCT company
FROM [payslips].[dbo].[myapp_user]
) au
);
DECLARE #sql nvarchar(max) = '
SELECT
au.email,
au.password,
au.GP_employee_id,
au.company,
slip_number = u.CHEKNMBR,
slip_number2 = CONVERT(date, u.CHEKDATE)
FROM [payslips].[dbo].[myapp_user] au
LEFT JOIN (
' + #unioned + '
) u ON u.company = au.company
AND u.EMPLOYID = au.GP_employee_id;
';
PRINT #sql; -- for testing
EXEC sp_executesql #sql;

Answer 2

DECLARE #sql VARCHAR(1000);
DECLARE #company VARCHAR(50);
DROP TABLE IF EXISTS #myapp_user;
CREATE TABLE #myapp_user
(
email VARCHAR(256),
[password] VARCHAR(256),
GP_employee_id INT,
slip_number INT,
slip_number2 INT
);
DECLARE db_cursor CURSOR FOR
SELECT DISTINCT company FROM [payslips].[dbo].[myapp_user];
OPEN db_cursor
FETCH NEXT FROM db_cursor INTO #company
WHILE ##FETCH_STATUS = 0
BEGIN
SET #sql = '
SELECT
email,
password,
GP_employee_id,
slip_number = (select distinct CHEKNMBR from ' + QUOTENAME(#company) + '.[dbo].[UPR30300] WHERE EMPLOYID = GP_employee_id and CHEKDATE > GETDATE() - 20),
slip_number2 = (select distinct CONVERT(date , CHEKDATE) from ' + QUOTENAME(#company) + '.[dbo].[UPR30300] WHERE EMPLOYID = GP_employee_id and CHEKDATE > GETDATE() - 20)
FROM
[payslips].[dbo].[myapp_user]';
INSERT INTO #myapp_user EXECUTE (#sql);
FETCH NEXT FROM db_cursor INTO #company;
END
CLOSE db_cursor
DEALLOCATE db_cursor
SELECT * FROM #myapp_user;