Loop through a recordset and use the result to do another SQL select and return the results - sql

Question

I am completely new to stored procedure. This time, I need to create a stored procedure in MS SQL.
Let's say I have the following table.
Table name: ListOfProducts
--------------------------
SomeID, ProductID
34, 4
35, 8
35, 11
How do I pass in a SomeID. Use this SomeID to select a recordset from table, ListOfProducts. Then loop through this record set.
Let's say I pass in SomeID = 35.
So, the record set will return 2 records with SomeID 35. In the loop, I will get ProductID 8 and 11, which will be used to do another select from another table.
The stored procedure should return the results from the 2nd select.
How can I do this in MS SQL stored procedure?
Sorry, for this newbie question. Thanks for any help.

Answer 1

If you want looping through the records. You can do like:
--Container to Insert Id which are to be iterated
Declare #temp1 Table
(
tempId int
)
--Container to Insert records in the inner select for final output
Declare #FinalTable Table
(
Id int,
ProductId int
)
Insert into #temp1
Select Distinct SomeId From YourTable
-- Keep track of #temp1 record processing
Declare #Id int
While((Select Count(*) From #temp1)>0)
Begin
Set #Id=(Select Top 1 tempId From #temp1)
Insert Into #FinalTable
Select SomeId,ProductId From ListOfProducts Where Id=#Id
Delete #temp1 Where tempId=#Id
End
Select * From #FinalTable

Answer 2

There is probably no point in writing an explicit loop if you don't need to preform some action on the products that can't be done on the whole set. SQL Server can handle stuff like this much better on its own. I don't know what your tables look like, but you should try something that looks more like this.
CREATE PROC dbo.yourProcName
#SomeID int
AS
BEGIN
SELECT
P.ProductId,
P.ProductName
FROM
Product P
JOIN
ListOfProducts LOP
ON LOP.ProductId = P.ProductId
WHERE
LOP.SomeId = #SomeID
END

Answer 3

I had to do something similar in order to extract hours from a select resultset start/end times and then create a new table iterating each hour.
DECLARE #tCalendar TABLE
(
RequestedFor VARCHAR(50),
MeetingType VARCHAR(50),
RoomName VARCHAR(MAX),
StartTime DATETIME,
EndTime DATETIME
)
INSERT INTO #tCalendar(RequestedFor,MeetingType,RoomName,StartTime,EndTime)
SELECT req as requestedfor
,meet as meetingtype
,room as rooms
,start as starttime
,end as endtime
--,u.datetime2 as endtime
FROM mytable
DECLARE #tCalendarHours TABLE
(
RequestedFor VARCHAR(50),
MeetingType VARCHAR(50),
RoomName VARCHAR(50),
Hour INT
)
DECLARE #StartHour INT,#EndHour INT, #StartTime DATETIME, #EndTime DATETIME
WHILE ((SELECT COUNT(*) FROM #tCalendar) > 0)
BEGIN
SET #StartTime = (SELECT TOP 1 StartTime FROM #tCalendar)
SET #EndTime = (SELECT TOP 1 EndTime FROM #tCalendar)
SET #StartHour = (SELECT TOP 1 DATEPART(HOUR,DATEADD(HOUR,0,StartTime)) FROM #tCalendar)
SET #EndHour = (SELECT TOP 1 DATEPART(HOUR,DATEADD(HOUR,0,EndTime)) FROM #tCalendar)
WHILE #StartHour <= #EndHour
BEGIN
INSERT INTO #tCalendarHours
SELECT RequestedFor,MeetingType,RoomName,#StartHour FROM #tCalendar WHERE StartTime = #StartTime AND EndTime = #EndTime
SET #StartHour = #StartHour + 1
END
DELETE #tCalendar WHERE StartTime = #StartTime AND EndTime = #EndTime
END

Answer 4

Do something like this:
Declare #ID int
SET #ID = 35
SELECT
p.SomeID
,p.ProductID
FROM ListOfProducts p
WHERE p.SomeID = #ID
-----------------------
--Or if you have to join to get it
Declare #ID int
SET #ID = 35
SELECT
c.SomeID
,p.ProductID
,p.ProductName
FROM ListOfProducts p
INNER JOIN categories c on p.ProductID = c.SomeID
WHERE p.SomeID = #ID

Answer 5

You can use option with WHILE loop and BREAK/CONTINUE keywords
CREATE PROC dbo.yourProcName
#SomeID int
AS
BEGIN
IF OBJECT_ID('tempdb.dbo.#resultTable') IS NOT NULL DROP TABLE dbo.#resultTable
CREATE TABLE dbo.#resultTable
(Col1 int, Col2 int)
DECLARE #ProductID int = 0
WHILE(1=1)
BEGIN
SELECT #ProductID = MIN(ProductID)
FROM ListOfProducts
WHERE SomeID = #SomeID AND ProductID > #ProductID
IF #ProductID IS NULL
BREAK
ELSE
INSERT dbo.#resultTable
SELECT Col1, Col2
FROM dbo.yourSearchTable
WHERE ProductID = #ProductID
CONTINUE
END
SELECT *
FROM dbo.#resultTable
END
Demo on SQLFiddle