Is there anyway to loop through a table variable in T-SQL?
DECLARE @table1 TABLE ( col1 int )
INSERT into @table1 SELECT col1 FROM table2
You can loop through the table variable or you can cursor through it. This is what we usually call a RBAR - pronounced Reebar and means Row-By-Agonizing-Row.
I would suggest finding a SET-BASED answer to your question (we can help with that) and move away from rbars as much as possible.
Following Stored Procedure loop through the Table Variable and Prints it in Ascending ORDER. This example is using WHILE LOOP.
CREATE PROCEDURE PrintSequenceSeries
-- Add the parameters for the stored procedure here
@ComaSeperatedSequenceSeries nVarchar(MAX)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
DECLARE @SERIES_COUNT AS INTEGER
SELECT @SERIES_COUNT = COUNT(*) FROM PARSE_COMMA_DELIMITED_INTEGER(@ComaSeperatedSequenceSeries, ',') --- ORDER BY ITEM DESC
DECLARE @CURR_COUNT AS INTEGER
SET @CURR_COUNT = 1
DECLARE @SQL AS NVARCHAR(MAX)
WHILE @CURR_COUNT <= @SERIES_COUNT
BEGIN
SET @SQL = 'SELECT TOP 1 T.* FROM ' +
'(SELECT TOP ' + CONVERT(VARCHAR(20), @CURR_COUNT) + ' * FROM PARSE_COMMA_DELIMITED_INTEGER( ''' + @ComaSeperatedSequenceSeries + ''' , '','') ORDER BY ITEM ASC) AS T ' +
'ORDER BY T.ITEM DESC '
PRINT @SQL
EXEC SP_EXECUTESQL @SQL
SET @CURR_COUNT = @CURR_COUNT + 1
END;
Following Statement Executes the Stored Procedure:
EXEC PrintSequenceSeries '11,2,33,14,5,60,17,98,9,10'
The result displayed in SQL Query window is shown below:
The function PARSE_COMMA_DELIMITED_INTEGER() that returns TABLE variable is as shown below :
CREATE FUNCTION [dbo].[parse_comma_delimited_integer]
(
@LIST VARCHAR(8000),
@DELIMITER VARCHAR(10) = ',
'
)
-- TABLE VARIABLE THAT WILL CONTAIN VALUES
RETURNS @TABLEVALUES TABLE
(
ITEM INT
)
AS
BEGIN
DECLARE @ITEM VARCHAR(255)
/* LOOP OVER THE COMMADELIMITED LIST */
WHILE (DATALENGTH(@LIST) > 0)
BEGIN
IF CHARINDEX(@DELIMITER,@LIST) > 0
BEGIN
SELECT @ITEM = SUBSTRING(@LIST,1,(CHARINDEX(@DELIMITER, @LIST)-1))
SELECT @LIST = SUBSTRING(@LIST,(CHARINDEX(@DELIMITER, @LIST) +
DATALENGTH(@DELIMITER)),DATALENGTH(@LIST))
END
ELSE
BEGIN
SELECT @ITEM = @LIST
SELECT @LIST = NULL
END
-- INSERT EACH ITEM INTO TEMP TABLE
INSERT @TABLEVALUES
(
ITEM
)
SELECT ITEM = CONVERT(INT, @ITEM)
END
RETURN
END
Here's my variant. Pretty much just like all the others, but I only use one variable to manage the looping.
DECLARE
@LoopId int
,@MyData varchar(100)
DECLARE @CheckThese TABLE
(
LoopId int not null identity(1,1)
,MyData varchar(100) not null
)
INSERT @CheckThese (MyData)
select MyData from MyTable
order by DoesItMatter
SET @LoopId = @@rowcount
WHILE @LoopId > 0
BEGIN
SELECT @MyData = MyData
from @CheckThese
where LoopId = @LoopId
-- Do whatever
SET @LoopId = @LoopId - 1
END
Raj More's point is relevant--only perform loops if you have to.
I didn't know about the WHILE structure.
The WHILE structure with a table variable, however, looks similar to using a CURSOR, in that you still have to SELECT the row into a variable based on the row IDENTITY, which is effectively a FETCH.
Is there any difference between using WHERE and something like the following?
DECLARE @table1 TABLE ( col1 int )
INSERT into @table1 SELECT col1 FROM table2
DECLARE cursor1 CURSOR
FOR @table1
OPEN cursor1
FETCH NEXT FROM cursor1
I don't know if that's even possible. I suppose you might have to do this:
DECLARE cursor1 CURSOR
FOR SELECT col1 FROM @table1
OPEN cursor1
FETCH NEXT FROM cursor1
Thanks for you help!
Add an identity to your table variable, and do an easy loop from 1 to the @@ROWCOUNT of the INSERT-SELECT.
Try this:
DECLARE @RowsToProcess int
DECLARE @CurrentRow int
DECLARE @SelectCol1 int
DECLARE @table1 TABLE (RowID int not null primary key identity(1,1), col1 int )
INSERT into @table1 (col1) SELECT col1 FROM table2
SET @RowsToProcess=@@ROWCOUNT
SET @CurrentRow=0
WHILE @CurrentRow<@RowsToProcess
BEGIN
SET @CurrentRow=@CurrentRow+1
SELECT
@SelectCol1=col1
FROM @table1
WHERE RowID=@CurrentRow
--do your thing here--
END
Here is my version of the same solution...
declare @id int
SELECT @id = min(fPat.PatientID)
FROM tbPatients fPat
WHERE (fPat.InsNotes is not null AND DataLength(fPat.InsNotes)>0)
while @id is not null
begin
SELECT fPat.PatientID, fPat.InsNotes
FROM tbPatients fPat
WHERE (fPat.InsNotes is not null AND DataLength(fPat.InsNotes)>0) AND fPat.PatientID=@id
SELECT @id = min(fPat.PatientID)
FROM tbPatients fPat
WHERE (fPat.InsNotes is not null AND DataLength(fPat.InsNotes)>0)AND fPat.PatientID>@id
end