Tsql union in while loop - sql

Question

I am trying to union the same table together with itself while changing some value in the where clause. The problem i have is with the union between the loops. I can not use a table variable since the schema is too complicated to write by hand each time. Temp tables seem to be the way to go but I do not know how to get it to work and the correct syntax.
psuedo code of what I am trying to achieve:
DECLARE #var int, #tempTable
SET #var = someValue
WHILE expressionIncludingVar
#tempTable = SELECT *
FROM someTable
WHERE column = #var
UNION ALL #tempTable
SET #var = someChangeToVar
RETRUN #tempTable
The result of the query should be #tempTable hence the weird "RETURN #tempTable".
Thank you in advance.
EDIT:
Another hardcoded example:
I am trying to unhardcode something like this:
SELECT someAggregateColumns
FROM table
WHERE someDateColumn > #date and < someDateColumn < DATEADD(month, 2, #date)
GROUP BY someColumn
UNION ALL
SELECT someAggregateColumns
FROM table
WHERE someDateColumn > DATEADD(month, 1, #date) and and < someDateColumn < DATEADD(month, 1, DATEADD(month, 3, #date))
GROUP BY someColumn
SELECT someAggregateColumns
FROM table
WHERE someDateColumn = DATEADD(month, 2, #date) DATEADD(month, 1, DATEADD(month, 4, #date))
GROUP BY someColumn
UNION ALL
....etc

Answer 1

Maybe Recursive CTE works for you.
You can try this.
DECLARE #MyTable TABLE(ID INT, ColumnA VARCHAR(10), ColumnB VARCHAR(10))
INSERT INTO #MyTable VALUES
(1,'A', '10'),
(2,'B', '11'),
(3,'C', '12'),
(4,'D', '13'),
(5,'E', '14'),
(6,'F', '15'),
(7,'H', '16')
DECLARE #var INT = 4
;WITH CTE AS (
SELECT * FROM #MyTable WHERE ID = #var
UNION ALL
SELECT T.* FROM CTE INNER JOIN #MyTable T ON CTE.ID - 1 = T.ID
)
SELECT * INTO #tempTable FROM CTE
SELECT * FROM #tempTable
DROP TABLE #tempTable

Answer 2

If the only thing what is different in each cycle is a counter, then why aren't you just write one query including all data?
Instead of WHERE column = #var use WHERE column >= 0 AND column <= #maxVarValue.
If your conditions are more complex, you should consider to have a small (temp) table which contains the columns to be filtered, then just join that table to your source to get the desired result.
According to the comments, you can use a tally table (or numbers table).
Example:
DECLARE #Tally (Number INT);
INSERT INTO #Tally (Number) VALUES (0),(1),(2),(3),(4),(5);
SELECT
someAggregateColumns
FROM
table AGG
INNER JOIN #Tally T
ON AGG.someDateColumn = DATEADD(month, T.Number, #date)
WHERE
T.Number >= 0
AND T.Number <= 3
;
The above query will return the results for the current and the next 3 months.
You can persist a numbers table and re-use it. I usually have one called util.Number.

Answer 3

based in second example what you want is
SELECT someAggregateColumns
FROM table
WHERE someDateColumn IN (
#date,
DATEADD(month, 1, #date),
DATEADD(month, 2, #date),
DATEADD(month, 3, #date)
)
GROUP BY someColumn
Now if you want a range is even easier:
WHERE someDateColumn BETWEEN #date
AND DATEADD(month, 3, #date)

Answer 4

Using a TALLY table and a CROSS APPLY you can generate the Dates to check:
DECLARE #Var INT = 4
DECLARE #Date Date = '2017-01-01'
;WITH Tally
AS
(
SELECT ROW_NUMBER() OVER (ORDER BY Object_Id) -1 AS Num
FROM sys.columns
)
SELECT *
FROM MyTable
CROSS APPLY Tally
WHERE Num < #var AND
MyDate = DATEADD(month, num, #date)