Looping distinct values from one table through another without a join

Question

I know looping is not ideal in SQL, but I couldn't think of another way of doing this.

I want each distinct row from this Table 1 to have each distinct date and hour produced on Table 2.

In other words, Table 2 has the dates between 05/01/2014 through 04/30/2015, with each distinct date having 24 rows, one for each hour of the day. I now want each distinct row in Table 1 to have each distinct date on Table 2, with each of its 24 hours.

Table 1:

DROP TABLE Baylor_Raw..MEDICAL_SERVICE_DESC
SELECT MEDICAL_SERVICE_DESC 
INTO Baylor_Raw..MEDICAL_SERVICE_DESC
FROM Baylor_Raw..Raw_ADT 
WHERE MEDICAL_SERVICE_DESC IS NOT NULL AND MEDICAL_SERVICE_DESC NOT IN ('#N/A','CANCEL','DAY SURGERY','HOSPICE','INFUSION')

Table 2:

DECLARE @DATE DATE
SET @DATE = '05/01/2014'

DECLARE @HOUR INT
SET @HOUR = 0

DROP TABLE Baylor_Raw..DateTable
CREATE TABLE Baylor_Raw..DateTable
    (DATE_OF_DISCHARGE DATE
    ,HOUR_OF_DISCHARGE INT)


WHILE @DATE<'05/01/2015' BEGIN
    WHILE @HOUR<25 BEGIN
        INSERT INTO Baylor_Raw..DateTable (DATE_OF_DISCHARGE,HOUR_OF_DISCHARGE)
        VALUES (@DATE,@HOUR)
        SET @HOUR = @HOUR+1
    END
    SET @DATE = DATEADD(DD,1,@DATE)
    SET @HOUR = 0
END

This below attempt did not work. I canceled after the run time exceeded several minutes.

DECLARE @MEDICAL_SERVICE_DESC NVARCHAR(255)
SET @MEDICAL_SERVICE_DESC = (SELECT MIN(MEDICAL_SERVICE_DESC) FROM Baylor_Raw..MEDICAL_SERVICE_DESC)

DECLARE @DATE DATE
SET @DATE = '05/01/2014'

DECLARE @HOUR INT
SET @HOUR = 0

DROP TABLE Baylor_Raw..DateTable
CREATE TABLE Baylor_Raw..DateTable
(MEDICAL_SERVICE_DESC NVARCHAR,
DATE_OF_DISCHARGE DATE
,HOUR_OF_DISCHARGE INT)

WHILE @MEDICAL_SERVICE_DESC IS NOT NULL BEGIN
    WHILE @DATE<'05/01/2015' BEGIN
        WHILE @HOUR<25 BEGIN
            INSERT INTO Baylor_Raw..DateTable (MEDICAL_SERVICE_DESC,DATE_OF_DISCHARGE,HOUR_OF_DISCHARGE)
            VALUES (@MEDICAL_SERVICE_DESC,@DATE,@HOUR)
            SET @HOUR = @HOUR+1
        END
        SET @DATE = DATEADD(DD,1,@DATE)
        SET @HOUR = 0
    END
DELETE FROM Baylor_Raw..MEDICAL_SERVICE_DESC WHERE MEDICAL_SERVICE_DESC = @MEDICAL_SERVICE_DESC
SET @MEDICAL_SERVICE_DESC = (SELECT MIN(MEDICAL_SERVICE_DESC) FROM Baylor_Raw..MEDICAL_SERVICE_DESC)
SET @DATE = '05/01/2014'
END

Answer 1

So you want all distinct records from table1 paired with all records in table2? That is a cross join:

select *
from (select distinct * from table1) t1
cross join table2;

Or do you want them related by date? Then inner-join:

select *
from (select distinct * from table1) t1
inner join table2 t2 on t1.date = t2.date;

Answer 2

You might get better performance from building lists of dates and hours using loops first, and then combining it with the service names just one time using a cross join, something like this. You may need to tweak it a bit because you understand the source data:

DECLARE @dates TABLE (DATE DATE)
DECLARE @hours TABLE (hours INT)
DECLARE @hour INT
    ,@date DATE

SET @hour = 0
SET @date = '05/01/2014'

WHILE (@hour < 25)
BEGIN
    INSERT INTO @hours
    SELECT @hour

    SET @hour = @hour + 1
END

WHILE (@ DATE < '05/01/2015')
BEGIN
    INSERT INTO @dates
    SELECT @date

    SET @DATE = DATEADD(DD, 1, @DATE)
END

INSERT INTO Baylor_Raw..DateTable (
    MEDICAL_SERVICE_DESC
    ,DATE_OF_DISCHARGE
    ,HOUR_OF_DISCHARGE
    )
SELECT MEDICAL_SERVICE_DESC
    ,DATE
    ,hour
FROM Baylor_Raw..MEDICAL_SERVICE_DESC
CROSS JOIN @date d
CROSS JOIN @hours h