how to update with a new variable
let's say I wanted to do the following
update T
set T.property1 = (declare #temp varch(20)
#temp = 'testing')
from #temp_table_name T
is this possible. I need to update a table but the new element is the end result of a series of complicated statements and it would be a lot easier to define some variables along the way to handle intermediate outputs. What is the correct syntax for what I'm trying to do above because it's not working
Is something like this what you're looking for?
DECLARE #temp varchar(20)
SET #temp = 'testing, or the result of a query maybe?'
UPDATE T SET T.property1 = #temp
FROM #temp_table_name T
WHERE 1 = 1
Move all of those statements into a scalar valued user-defined function and then in your update statement do this:
update T
set T.property1 = dbo.myUdf(...)
from #temp_table_name T
where ... are any parameters it may need from the row to do its job.
Related
I was wondering if it is possible to set a declared variable to a return value from a select result? Something like:
#WatchedSeconds
SET #WatchedSeconds = 200
DECLARE #SelectedVideo int
SET #SelectedVideo = (SELECT TOP 1 * FROM Video v WHERE v.VideoID = 12)
IF #SelectedVideo IS NOT NULL
BEGIN
IF #SelectedVideo.VideoLength = #WatchedSeconds
BEGIN
--DO SOMETHING
END
IF #SelectedVideo.SomeOtherColumn = #SomethingElse
BEGIN
END
END
It's for using some information from the SELECT result multiple places in a Stored Procedure.
I know that I can set a variable to e.g, a integer, and set it to the selected result, if it returns a integer, e.g:
DECLARE #VideoSeconds int
SET #VideoSeconds = (SELECT v.Length FROM Video v WHERE v.VideoID = #VideoID)
This way I have to make multiple variables, and multiple SELECT calls if I need to use more values from the Video result. And that's what I want to avoid.
You can do this simply by running:
SELECT #videoSeconds = v.Length FROM Video v WHERE v.VideoID = #VideoID
so as to not add the SET part.
Also, you must make sure that only 1 row is being returned by the query, otherwise it will generate an error.
You can try something like
(declare variables first...)
SELECT TOP 1 #var1=col1, #var2=col2, #var3=col3, [...] FROM YourTable WHERE YourFilter
EDIT: All together this seems not to be the best approach... With SQL you should not think in values and single rows but rather in result sets (set based programming). Your thinking leads to many tiny selects, while loops, cursors and all this stuff one should avoid.
You can store the results in a temporary table or table variable:
SELECT TOP 1 *
INTO #SelectedVideo
FROM Video v
WHERE v.VideoID = 12;
Then you can assign values from the table later in your code. Something like:
IF ( (SELECT VideoLength FROM #SelectedVideo) = #WatchedSeconds)
However, for your particular example, if you have an index on video(VideoId), then there is little to be gained performance-wise from using a temporary table.
If what you're trying to get is similar to returning a dataset in a procedural language (so you can type something like Result.Field1 = 'Test') then I don't think this is possible. You'll just need to declare multiple variables and make the SELECT call as
SELECT TOP 1 #var1=col1, #var2=col2, #var3=col3, [...] FROM YourTable WHERE YourFilter
as #Shnugo suggests
The 'dataset' equivalent structure in SQL is cursors, but they require variables to be set up as well, so there's no benefit there.
I have a merge statement that should update or insert a single record always. I want to remember the ID of that statement in a variable. It looks like this:
DECLARE #int int
MERGE dbo.table AS A
USING (SELECT 'stringtomatch' AS string) AS B ON B.string= A.string
WHEN MATCHED THEN
UPDATE SET somecolumn = 'something'
WHEN NOT MATCHED THEN
INSERT
VALUES ('stringtomatch',
'something')
OUTPUT #int = inserted.ID;
Now this doesen't work because you can't set #int in the output clause this way. I know I could create a temptable and use INTO #temptable in the output. But since I know it's always a single record I want to have the ID in a INT variable.
Is this even possible? Or am I forced to use a table variable.
How?
No, you have to use a table variable with OUTPUT
However, you can do this...
...
WHEN MATCHED THEN
UPDATE
SET
#int = ID,
somecolumn = 'something'
WHEN NOT MATCHED THEN
INSERT
VALUES ('stringtomatch',
'something');
SET #int = ISNULL(#int, SCOPE_IDENTITY());
The "assign in UPDATE" has been a valid syntax for SQL Server for a long time. See MERGE on MSDN too. Both say this:
...<set_clause>::=
SET
...
#variable=expression
I need to use a temporary variable declared in stored procedure. I need to use this variable to assign a value and do some function in a Matched statement. How can I use? is there any other way to have value??
Thanks in advance
This is how you can define a local variable in SQL Server:
DECLARE #MyVariable INT
SET #MyVariable = 12
SELECT HouseNumber + #MyVariable as NewHouseNumber FROM MyTable WHERE Id = 1
If you declare the variable preceding the MERGE statement then you can indeed use that variable within the MERGE statement. This apples to table variables as well as scalar variables.
I think he ment something like this
MERGE TargetTable as tar
USING SourceTable as src
ON tar.SomeID = src.OtherID
DECLARE #BossId INT
SET #BossId = (SELECT ID FROM EmployeeTable WHERE [BossID] = src.BossID)
--Here we take dynamicly an ID from another table
WHEN NOT MATCHED THEN
INSERT (list OF fields, [BossID])
VALUES (list OF values, #BossId)
WHEN MATCHED THEN
UPDATE
SET (list OF SET statements);
This way in every INSERT statement will have different BossID. Is this even possible? If not - How to insert records this way? Imagine that the SourceTable (which in my case is an input parameter in a SP) came with ID which needs to be mapped with another talbe. Any suggestions?
My post is more like an addition to the original question.
I'm converting some data in SQL Server 2005. I have a table update like this:
update Invoices set Invoices.InvoiceReference = 'NewRef'
where Invoices.InvoiceReference='Unknown'
But what I'd like to plug in instead of 'NewRef' is the output from a stored procedure that uses parameters from the columns of the Invoices table. The stored procedure itself does updates to another table. Is it possible? Something like this below (which is wrong of course :)
DECLARE #Ref nvarchar(20)
update Invoices set Invoices.InvoiceReference = (
EXEC InvoiceGenerateRef
#ClientCode = Invoices.ClientCode,
#EventCode = Invoices.EventCode,
#Ref = #Ref OUTPUT
SELECT #Ref)
where Invoices.InvoiceReference='Unknown'
Do I need to use a cursor or is the syntax just wrong?
Thanks,
Chris.
I think you would be better off changing your stored procedure into either a function or a view (depending on what you actually do in the proc).
I think what you are after is to join to the resultset of a stored proc which would not work.
You are almost there, the correct way to achieve what you are looking to do would be to define an output parameter as part of your stored procedure definition.
This paramter can then be used as part of your update statement.
DECLARE #Ref nvarchar(20)
EXEC InvoiceGenerateRef
#ClientCode = N'ABC2',
#EventCode = N'X1'
#Ref = #Ref OUTPUT
update Invoices
set Invoices.InvoiceReference = #Ref
where Invoices.InvoiceReference='Unknown'
by using OPENROWSET you can query your stored procedure results just like a view:
http://blogs.technet.com/wardpond/archive/2005/08/01/the-openrowset-trick-accessing-stored-procedure-output-in-a-select-statement.aspx
so for your case this might be useful.
1) You could change InvoiceGenerateRef so that it could optionally save the generated Ref into InvoiceReference field. Presumably you would also have to provide parameters to define the selection
2) You could us e cursor to step round each row in
SELECT ...
FROM Invoices
WHERE Invoices.InvoiceReference='Unknown'
and pass the details to InvoiceGenerateRef and then update the row. This is bad IMHO and will be slow (Your best bet is a set-based solution)
3) You could select the appropriate Invoices.ID's into a temporary table which would be in scope for the InvoiceGenerateRef so that it could iterate that (i.e. the choice of WHICH rows to update is external to the SProc, but the SProc does the actual updating)
CREATE TABLE #TEMP
(
T_ID int NOT NULL
)
INSERT INTO #TEMP (T_ID)
SELECT ID
FROM Invoices
WHERE Invoices.InvoiceReference='Unknown'
EXEC InvoiceGenerateRef #ACTION='UpdateFromTemporaryTable'
4) You could change InvoiceGenerateRef to a function that performed the same task:
UPDATE U
SET U.InvoiceReference =
dbo.MyInvoiceGenerateRefFunction(U.ClientCode, U.EventCode)
FROM Invoices AS U
WHERE U.InvoiceReference='Unknown'
MyInvoiceGenerateRefFunction would have to be deterministic (I think!)
This would be my preferred choice
I'm not sure if this is something I should do in T-SQL or not, and I'm pretty sure using the word 'iterate' was wrong in this context, since you should never iterate anything in sql. It should be a set based operation, correct? Anyway, here's the scenario:
I have a stored proc that returns many uniqueidentifiers (single column results). These ids are the primary keys of records in a another table. I need to set a flag on all the corresponding records in that table.
How do I do this without the use of cursors? Should be an easy one for you sql gurus!
This may not be the most efficient, but I would create a temp table to hold the results of the stored proc and then use that in a join against the target table. For example:
CREATE TABLE #t (uniqueid int)
INSERT INTO #t EXEC p_YourStoredProc
UPDATE TargetTable
SET a.FlagColumn = 1
FROM TargetTable a JOIN #t b
ON a.uniqueid = b.uniqueid
DROP TABLE #t
You could also change your stored proc to a user-defined function that returns a table with your uniqueidentifiers. You can joing directly to the UDF and treat it like a table which avoids having to create the extra temp table explicitly. Also, you can pass parameters into the function as you're calling it, making this a very flexible solution.
CREATE FUNCTION dbo.udfGetUniqueIDs
()
RETURNS TABLE
AS
RETURN
(
SELECT uniqueid FROM dbo.SomeWhere
)
GO
UPDATE dbo.TargetTable
SET a.FlagColumn = 1
FROM dbo.TargetTable a INNER JOIN dbo.udfGetUniqueIDs() b
ON a.uniqueid = b.uniqueid
Edit:
This will work on SQL Server 2000 and up...
Insert the results of the stored proc into a temporary table and join this to the table you want to update:
INSERT INTO #WorkTable
EXEC usp_WorkResults
UPDATE DataTable
SET Flag = Whatever
FROM DataTable
INNER JOIN #WorkTable
ON DataTable.Ket = #WorkTable.Key
If you upgrade to SQL 2008 then you can pass table parameters I believe. Otherwise, you're stuck with a global temporary table or creating a permanent table that includes a column for some sort of process ID to identify which call to the stored procedure is relevant.
How much room do you have in changing the stored procedure that generates the IDs? You could add code in there to handle it or have a parameter that lets you optionally flag the rows when it is called.
Use temporary tables or a table variable (you are using SS2005).
Although, that's not nest-able - if a stored proc uses that method then you can't dumpt that output into a temp table.
An ugly solution would be to have your procedure return the "next" id each time it is called by using the other table (or some flag on the existing table) to filter out the rows that it has already returned
You can use a temp table or table variable with an additional column:
DECLARE #MyTable TABLE (
Column1 uniqueidentifer,
...,
Checked bit
)
INSERT INTO #MyTable
SELECT [...], 0 FROM MyTable WHERE [...]
DECLARE #Continue bit
SET #Continue = 1
WHILE (#Continue)
BEGIN
SELECT #var1 = Column1,
#var2 = Column2,
...
FROM #MyTable
WHERE Checked = 1
IF #var1 IS NULL
SET #Continue = 0
ELSE
BEGIN
...
UPDATE #MyTable SET Checked = 1 WHERE Column1 = #var1
END
END
Edit: Actually, in your situation a join will be better; the code above is a cursorless iteration, which is overkill for your situation.