I want to create a function in SQL Server which takes a comma separated string a parameter, splits it and returns one value at a time. The basic idea here is to call that function from a query. Something like this.
CREATE FUNCTION SPLIT_VALUE(#IN_CSV)
RETURN VARCHAR AS
-- LOGIC TO RETURN A SINGLE VALUE FROM CSV
END
I want to call this function from a stored procedure.
CREATE PROCEDURE DEMO_PROC #IN_CSV VARCHAR(5000), #OUT VARCHAR(5000) OUTPUT AS
BEGIN
SELECT #OUT= CONCAT(A.VALUE1,B.VALUE2) FROM TABLE1 A INNER JOIN TABLE2 B ON A.ID=B.ID WHERE A.ID
IN(--CALL THE FUNCTION AND GET ONE VALUE);
END;
I have to create a loop or cursor to point to a particular value every time. Is this practically possible to? If yes then how can I do that?
Like I mention, you'll have to use a CURSOR to do this, however, the fact you want to do it this way infers a (large) design flaw:
DECLARE #value varchar(8000)
DECLARE Delimited_Values CURSOR FAST_FORWARD
FOR
SELECT [value]
FROM STRING_SPLIT('a,b,c,d,e',',')
OPEN Delimited_Values;
FETCH NEXT FROM Delimited_Values
INTO #value;
WHILE ##FETCH_STATUS = 0 BEGIN
SELECT #value; --Do your stuff here
FETCH NEXT FROM Delimited_Values
INTO #value;
END;
CLOSE Delimited_Values;
DEALLOCATE Delimited_Values;
Related
I have to put a result of a query (single column and value is being pulled) into a variable. I'm trying to use a cursor however I choose the database to query based on a variable here is my query
SELECT productName, price FROM #ShopName.dbo.Products WHERE ProductName = #ProductName
#ShopName variable is being pulled from the database first and assigned to the variable using a cursor. #ProductName variable is being populated by an input parameter coming from API. I have to get ProductName from a specific database (there are multiple databases with products), but the query above throws syntax errors. Additionally when I tried ad hoc query assigned to a variable:
SET #Sql = N'SELECT productName, price FROM ' + QUOTENAME(#ShopName) + '.dbo.Products WHERE ProductName = ' + #ProductName
It doesn't allow to use it in
DECLARE cursorT CURSOR
FOR
#Sql
This throws Incorrect syntax near '#Sql', Expecting '(', SELECT, or WITH
Is there any way to make it possible to use that query in cursor while using the variable with database name in it?
Cursors should be right at the bottom of your bag of techniques, used sparingly and with great care, only when necessary. I can't tell if it's necessary in your case, there's not enough code to know. But I wanted to get that out before continuing.
As a point of purely academic interest, yes, there are some ways you can do this. Two main ways:
Declare a cursor in the dynamic SQL, as Dale suggested. You can still use the cursor in static code which follows the declaration if the cursor is global.
Use dynamic SQL to drop the results into something with scope outside of the dynamic sql, like a temp table. The cursor over the temp table.
1 is just bad. It is likely to result in code which is extremely difficult to understand in future. I include it for curiosity only. 2 is reasonable.
Examples:
-- some dummy schema and data to work with
create table t(i int);
insert t values(1), (2);
-- option 1: declare a cursor dynamically, use it statically (don't do this)
declare #i int;
exec sp_executesql N'declare c cursor global for select i from t';
open c;
fetch next from c into #i;
while (##fetch_status = 0)
begin
print #i;
fetch next from c into #i;
end
close c;
deallocate c;
-- option 2: dynamically dump data to a table, eg a temp table
create table #u(i int);
exec sp_executesql N'insert #u (i) select i from t';
declare c cursor local for select i from #u;
declare #i int;
open c;
fetch next from c into #i;
while (##fetch_status = 0)
begin
print #i;
fetch next from c into #i;
end
close c;
deallocate c;
For a homework assignment, I'm trying to build a trigger that allows for multiple inserts/updates/deletes by utilizing a cursor. We have to use a cursor in order to practice the syntax. We know that there are very few practical scenarios for cursors in a production environment.
Here's what I'm trying to accomplish:
For each row inserted into the TAL_ORDER_LINE table, update the ON_HAND value in the TAL_ITEM table by subtracting the NUM_ORDERED value from the stored ON_HAND value.
Table Structure:
Current Query:
ALTER TRIGGER update_on_hand
ON TAL_ORDER_LINE
AFTER INSERT AS
DECLARE #vItemNum as char
DECLARE #vNumOrdered as int
DECLARE new_order CURSOR FOR
SELECT ITEM_NUM, NUM_ORDERED
FROM inserted
OPEN new_order;
FETCH NEXT FROM new_order INTO #vItemNum, #vNumOrdered;
WHILE ##FETCH_STATUS=0
BEGIN
UPDATE TAL_ITEM
SET ON_HAND = ON_HAND - #vNumOrdered
WHERE ITEM_NUM = #vItemNum
FETCH NEXT FROM new_order INTO #vItemNum, #vNumOrdered;
END
CLOSE new_order
DEALLOCATE new_order
My Insert Query:
INSERT INTO TAL_ORDER_LINE (ORDER_NUM, ITEM_NUM, NUM_ORDERED, QUOTED_PRICE)
VALUES (51626, 'KL78', 10, 10.95), (51626, 'DR67', 10, 29.95)
It runs successfully, but does not affect the ON_HAND value. I think the biggest problem is that I'm struggling to understand cursor syntax, especially the INTO clause in the FETCH statement and how data from the 'inserted' table is passed into the cursor. What do I need to know to get this to work? Thanks in advance!
Your problem is likely due to this:
DECLARE #vItemNum as char
it is HIGHLY unlikely that the ItemNum column is a single character. For future reference, you should always verify that you variable definitions are consistent with the values you expect to store in them. And as has been hinted - you will get better answers by posting a complete script rather than a picture.
Big question,how you gonna debug ?
Is On_Hand col NULL , then do this isnull(on_Hand,0)
DECLARE #vItemNum as char
DECLARE #vNumOrdered as int
DECLARE new_order CURSOR FOR
SELECT ITEM_NUM, NUM_ORDERED
FROM TAL_ORDER_LINE
OPEN new_order;
FETCH NEXT FROM new_order INTO #vItemNum, #vNumOrdered;
WHILE ##FETCH_STATUS=0
BEGIN
--UPDATE TAL_ITEM
--SET ON_HAND = ON_HAND - #vNumOrdered
--WHERE ITEM_NUM = #vItemNum
print #vItemNum
print vNumOrdered
FETCH NEXT FROM new_order INTO #vItemNum, #vNumOrdered;
END
CLOSE new_order
DEALLOCATE new_order
Try this :
ALTER TRIGGER update_on_hand ON TAL_ORDER_LINE
FOR INSERT AS
BEGIN
UPDATE TI
SET TI.ON_HAND = TI.ON_HAND - I.NUM_ORDERED
TAL_ITEM TI INNER JOIN
INSERTED I ON I.ITEM_NUM = TI.ITEM_NUM
END
Changed Trigger to FOR INSERT Trigger
Removed Cursor
Note: NOT Tested. ( If you post the sql scripts for create table + sample inserts I can give it a try )
I have a table with 700 rows. What I want to do is, to execute `select * from table_name' query on it and whatever result I will get want to store it in a variable and after that is done, want to traverse through each record for processing purpose? How do I achieve it? Any help??
Thanks in adv,
-saurabh
you want something which is called cursors
Cursors
You use a cursor to fetch rows returned by a query. You retrieve the rows into the cursor using a query and then fetch the rows one at a time from the cursor.
Steps
Declare variables to store the column values for a row.
Declare the cursor, which contains a query.
Open the cursor.
Fetch the rows from the cursor one at a time and store the column values in the variables declared in Step 1. You would then do something with those variables; such as display them on the screen, use them in a calculation, and so on.
Close the cursor.
hopefully this might help you cursor
here is an example I use to start with
USE pubs
GO
-- Declare the variables to store the values returned by FETCH.
DECLARE #au_lname varchar(40), #au_fname varchar(20)
DECLARE authors_cursor CURSOR FOR
SELECT au_lname, au_fname FROM authors
--WHERE au_lname LIKE 'B%'
ORDER BY au_lname, au_fname
OPEN authors_cursor
-- Perform the first fetch and store the values in variables.
-- Note: The variables are in the same order as the columns
-- in the SELECT statement.
FETCH NEXT FROM authors_cursor
INTO #au_lname, #au_fname
-- Check ##FETCH_STATUS to see if there are any more rows to fetch.
WHILE ##FETCH_STATUS = 0
BEGIN
-- Concatenate and display the current values in the variables.
PRINT #au_fname
-- This is executed as long as the previous fetch succeeds.
FETCH NEXT FROM authors_cursor
INTO #au_lname, #au_fname
END
CLOSE authors_cursor
DEALLOCATE authors_cursor
GO
I need some tip on tuning some TSQL to execute faster, it's taking way too long although it works. This may be because I'm fetching a key from another table before I can do the insert, any ideas anyone?
DECLARE db_cursorReads CURSOR FOR SELECT
[MeterId]
,[MeterRead]
FROM MdsReadsImports;
declare #PremiseMeterId int;
declare #MeterId nvarchar(24);
declare #MeterRead int;
OPEN db_cursorReads;
FETCH NEXT FROM db_cursorReads INTO
#MeterId
,#MeterRead;
WHILE ##FETCH_STATUS = 0
BEGIN
set #PremiseMeterId = (select top 1 PremiseMeterId from PremiseMeters where MeterId = #MeterId)
insert into PremiseMeterReads (MeterRead,PremiseMeterId)
values (#MeterRead, #MPremiseMeterId)
FETCH NEXT FROM db_cursorReads INTO
#MeterId
,#MeterRead;
END;
CLOSE db_cursorReads;
DEALLOCATE db_cursorReads;
I see you are retrieving PremiseMeterId but not using it in the script you posted. Perhaps you can ditch the cursor and perform a single set-based query:
INSERT INTO PremiseMeterReads (MeterRead,MeterId)
SELECT
[MeterRead]
,[MeterId]
FROM MdsReadsImports;
First, I note that you are setting but not using #PremiseMeterID.
Second, you seem to be doing this:
insert into PremiseMeterReads (MeterRead, MeterId)
select MeterRead, MeterId
from MdsReadsImports;
A set based operation should be much faster than using a cursor.
For the application I work on... we're creating a custom logging system. The user can view logs and apply "Tags" to them (Just like how you can apply tags to questions here!)
In this example, I'm trying to get a list of all the Logs given a "Tag." I realize I can accomplish this by using joins... but this is also an exercise for me to learn Stored Procedures a little better :)
I have a stored procedure that looks something like this to select a log by the PK
ALTER PROCEDURE [dbo].[getLogByLogId]
-- Add the parameters for the stored procedure here
#ID int
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- Insert statements for procedure here
SELECT TOP 1
LOG_ID,
a.A,
a.B,
a.C
FROM dbo.LOG a
WHERE a.LOG_ID = #ID
Now I would like to call this Stored Procedure from another... something like this
ALTER PROCEDURE [dbo].[getLogsByTagName]
-- Add the parameters for the stored procedure here
#TAG nvarchar(50)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- Insert statements for procedure here
SELECT TOP 1000
LOG_ID --somehow store this and execute the dbo.getLogByLogId procedure here
FROM dbo.LOG_TAG a
WHERE a.TAG = #TAG
Thanks
If you have complex logic in your logbyid SP which you are trying to avoid reproducing in multiple places in your system (choice of columns, derived columns, etc), I would recommend turning that into an inline table-valued function instead (potentially without taking the ID parameter, in which case, you can actually use an ordinary view).
Then you can either join to that ITVF/view in your other stored proc (or also make another udf) which does the search or use the OUTER APPLY functionality (not as efficient).
Inline table-valued functions are basically parameterized views and can be optimized fairly easily by the optimizer.
If you want to call another sproc from within a sproc just use:
CREATE PROCEDURE myTestProc
AS
BEGIN
--Do some work in this procedure
SELECT blah FROM foo
--now call another sproc
EXEC nameOfSecondSproc
END
The only way you can achive what you are attempting is by using a CURSOR.
If this is for your learning only, then by all means, give this a go, but I would not recomend this for production.
It would go something like this
DECLARE #Table TABLE(
ID INT
)
INSERT INTO #Table SELECT 1
INSERT INTO #Table SELECT 2
INSERT INTO #Table SELECT 3
INSERT INTO #Table SELECT 4
INSERT INTO #Table SELECT 5
INSERT INTO #Table SELECT 6
DECLARE Cur CURSOR FOR
SELECT ID
FROM #Table
OPEN Cur
DECLARE #ID INT
FETCH NEXT FROM Cur INTO #ID
WHILE ##FETCH_STATUS = 0
BEGIN
PRINT #ID
FETCH NEXT FROM Cur INTO #ID
END
CLOSE Cur
DEALLOCATE Cur
By using the #ID retrieved in the WHILE loop, you can then execute the sp you wish and insert the values into a table variable.
INSERT INTO #Table EXEC sp_MySP #ID
You can call a stored procedure from another using the following syntax:
ALTER PROCEDURE [dbo].[getLogsByTagName]
-- Add the parameters for the stored procedure here
#TAG nvarchar(50)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- Insert statements for procedure here
SELECT TOP 1000
LOG_ID --somehow store this and execute the dbo.getLogByLogId procedure here
FROM dbo.LOG_TAG a
WHERE a.TAG = #TAG
-- Execute dbo.getLogByLogId stored procedure
DECLARE #logId INTEGER
SET #logId = <some value>
EXEC dbo.getLogByLogId #logId
END
However, the difficult part of your question is that your dbo.getLogByLogId procedure can only accept a single LogID parameter and therefore will only be able to return a single Log record. You need to return information for all Logs where the LogId has a corresponding record in the Tags table.
The correct way to do this would be to JOIN the Log and Tag tables together, like so:
SELECT *
FROM dbo.LOG_TAG a
INNER JOIN dbo.LOG b ON a.LOG_ID = b.LOG_ID
WHERE a.TAG = #TAG
If you are concerned about returning the same logId multiple times, you can use the DISTINCT keyword in the SELECT statement to filter out the duplicated logIds.
You may also be able to rewrite your dbo.getLogByLogId procedure as a user-defined function (UDF). UDFs can accept a table as a parameter and return a table result.
An introduction to user-defined functions can be found in this article.