Question

I have table in SQL Server DB:

ID    Open_date     Close_date
1     01-01-2010    01-03-2010
2     21-01-2011    12-02-2011
3     01-03-2010    NULL
4     10-01-2010    NULL

I need to make some T-SQL query that will return:

Month    Year    Open    Close
01       2010    2       0
02       2010    0       0
03       2010    0       1
04       2010    0       0
05       2010    0       0
06       2010    0       0
07       2010    0       0
08       2010    0       0
09       2010    0       0
10       2010    0       0
11       2010    0       0
12       2010    0       0
01       2011    1       0
02       2011    0       1

Amount of entries in result set equals amount of months between min value from both ‘Open_date’ and ‘Close_date’ columns of table from DB and max value from same columns. The problem is how to find min and max value from two date columns, then generate dates from min to max and then use this temporary table(or what it would be) to count number of open and closed entries for every date from temporary table.

Answer 1

I changed the dates a bit, since I’m using a different date system, but this should work. Accept if it does, please!

DECLARE @TABLE1 TABLE
(
    ID INT
    , Open_date DATETIME
    , Close_date DATETIME
)

INSERT INTO @TABLE1 (ID, Open_date, Close_date)
      SELECT 1, '01-01-2010', '03-01-2010'
UNION SELECT 2, '01-21-2011', '02-12-2011'
UNION SELECT 3, '03-01-2010', NULL
UNION SELECT 4, '01-10-2010', NULL


DECLARE @MIN_DATE DATETIME
DECLARE @MAX_DATE DATETIME

SELECT @MIN_DATE = MIN(d)
    , @MAX_DATE = MAX(d)
FROM
(
    SELECT Open_date AS d
    FROM @TABLE1

        UNION

    SELECT Close_date AS d
    FROM @TABLE1
)a

--SELECT @MIN_DATE, @MAX_DATE



DECLARE @DATES TABLE
(
    ID INT IDENTITY(1,1)
    , [date] DATETIME
)

DECLARE @DATE DATETIME
SET @DATE = @MIN_DATE

WHILE (@DATE <= @MAX_DATE)
BEGIN

    INSERT INTO @DATES ([date])
    VALUES (@DATE)

    SET @DATE = @DATE + 1

END

--SELECT *
--FROM @DATES

SELECT MONTH(a.[date]) AS [Month]
    , YEAR(a.[date]) AS [Year]
    , SUM(CASE WHEN b.Open_date IS NOT NULL THEN 1 ELSE 0 END) AS [Open]
    , SUM(CASE WHEN b.Close_date IS NOT NULL THEN 1 ELSE 0 END) AS [Close]
FROM @DATES a
LEFT JOIN @TABLE1 b
    ON a.[date] = b.Open_date
GROUP BY YEAR(a.[date]), MONTH(a.[date])
ORDER BY YEAR(a.[date]), MONTH(a.[date])