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How to loop statements in SQL Server
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Closed 4 years ago.
How to implement a while loop in SQL server based on the below condition.
Then I need to execute select statement which returns ITEM_CODE ,It may have multiple rows too.
What I want to do inside the while loop is for each ITEM_CODE I need to get data from other tables (including joins ) and insert those data to a table .This loop will get end the count based on the first statements return.
Sample query structure:
SELECT ITEM_CODE //While loop must execute the count of this rows
FROM 'TABLE_1'
WHERE ITEM_AVAILABILITY = 'TRUE'
This statement will return a single row or may return multiple rows .
I need to pass this ITEM_CODE to the while loop each time .Inside the while loop I will get the values from multiple tables and insert it to another table.
WHILE (#COUNT <>0){
//Need to have the ITEM_CODE while looping each time.
//Get data from multiple tables and assign to variables (SET #VARIABLES)
//Insert statement
IF (#COUNT = #COUNT)
BREAK;
}
Is it possible with SQL server ,If Yes,please help me to fix this .
Try this:
DECLARE #DataSource TABLE
(
[ITEM_CODE] VARCHAR(12)
);
INSER INTO #DataSource ([ITEM_CODE])
SELECT ITEM_CODE //While loop must execute the count of this rows
FROM 'TABLE_1'
WHERE ITEM_AVAILABILITY = 'TRUE';
DECLARe #CurrentItemCode VARCHAR(12);
WHILE(EXISTS (SELECT 1 FROM #DataSource))
BEGIN;
SELECT TOP 1 #CurrentItemCod = [ITEM_CODE]
FROM #DataSource
--
--
DELETE FROM #DataSource
WHERE [ITEM_CODE] = #CurrentItemCod;
END;
The idea is to perform a loop while there is data in our buffer table. Then in each iteration of the loop, get one random item code value, perform your internal operations and delete the value from the buffer.
Some people are using row ID column in the buffer table, for example INT IDENTITY(1,1) and are selecting the first element, doing the internal operations and then deleting by id. But you need to know the count of the records and to increment the id with each iteration - something like for cycle.
Related
I am inserting parent records and child records at the same time in a stored procedure.
Rather than have outside code make nested calls to create each parent and then each child of that parent (which is even slower than my current approach), I am giving the sql a comma separated list of child types that I put into a temp table (#TempParentChildUpdateTable) which is associated with a parent record in a table value parameter (#PenguinParentChildUpdate).
Then I loop through both, insert the parent and then insert all related children.
The problem is this while loop is not performing very well at 13 requests per second.
How do I make this faster? How do I take out the while loop?
Is there a way to do this with non-looping inserts? If so, can the string parsing happen inside the inner insert?
DECLARE #RowCnt int = 0;
DECLARE #CounterId int = 1;
SELECT #RowCnt = COUNT(*) FROM #PenguinParentChildUpdate;
WHILE #CounterId <= #RowCnt
BEGIN
SELECT #GrandparentId = WorkflowInstanceId,
#ParentType = ParentType,
#ChildIds = ChildIds
FROM #PenguinParentChildUpdate
-- insert parent record
INSERT INTO WorkflowInstanceRole (ParentType, GrandparentId)
VALUES(#ParentType, #GrandparentId)
SET #ParentId = SCOPE_IDENTITY()
-- identify children
-- convert comma separated list (e.g. 4,91,12,6) into separate rows
INSERT INTO #TempParentChildUpdateTable (sq.ChildId, sq.ParentId)
select convert(int, value) ChildId, #ParentId RoleId FROM string_split(#ChildIds, CHAR(44))
-- insert children 7787+ =
IF (#ChildIds IS NOT NULL AND LEN(LTRIM(RTRIM(#ChildIds))) > 0)
BEGIN
INSERT INTO dbo.PenguinParentChild
(
grandparentId,
childid,
)
select
#ParentId,
childId,
from
#TempParentChildUpdateTable tsru
where
tsru.ParentId = #ParentId
END
SET #CounterId = #CounterId + 1
END
I am struggling to follow some of the logic in the loop, but I think the premise is
Insert to WorkFlowInstanceRole
Capture the inserted records then insert further children based on this.
Since step 2 requires data that is not in WorkFlowInstanceRole you need to use MERGE to add the new rows, rather than a standard insert. What this allows you to do is capture the ChildIds from the source table, even though you aren't inserting them. Something like this should do it (I've had to guess at some data types):
DECLARE #Output TABLE
(
ParentId INT,
ParentType INT,
GrandParentId INT,
ChildIDs VARCHAR(MAX)
);
MERGE INTO WorkflowInstanceRole AS t
USING #PenguinParentChildUpdate AS s
ON 1 = 0 -- Will never be true so will always insert
WHEN NOT MATCHED THEN
INSERT (ParentType, GrandparentId)
VALUES (s.ParentType, s.WorkflowInstanceId)
OUTPUT inserted.ParentId, inserted.ParentType, inserted.GrandParentId, s.ChilDIds
INTO #Output (ParentId,ParentType, GrandParentId, ChildIDs);
INSERT INTO dbo.PenguinParentChild (GrandParentId, ChildId)
SELECT o.ParentId,
CONVERT(int, ss.value)
FROM #Output AS o
CROSS APPLY STRING_SPLIT(i.ChileIds, CHAR(44)) AS ss;
The key part is the MERGE* really, since the condition is 1=0 then this will always insert. Unlike INSERT the OUTPUT clause on a merge will allow you to capture both the newly inserted identity value, and the non-inserted ChildIds column.
This is output into a temporary table, which you can then use, along with CROSS APPLY STRING_SPLIT() to insert the child records.
There may be some data errors, and logic may not be 100% perfect, but this should hopefully be a bit step in the right direction.
*MERGE has a number of known bugs, and I'd generally advise to steer clear, but I am not aware of any alternative that would allow you to capture the newly inserted identity value, and the non-inserted ChildIds column, and as far as I am aware none of these bugs affect this operation (Anecdotally, in that I have never encountered an issue using this method).
We are inserting bulk data into one of our database tables using SQL Server Management studio. Currently we are in a position where the data being sent to the database will be added to a particular row in a table (this is controlled by a stored procedure). What we are finding is that a timeout is occurring before the operation completes; at this point we think the operation is slow because of the while loop but we're unsure of how to approach writing a faster equivalent.
-- Insert statements for procedure here
WHILE #i < #nonexistingTblCount
BEGIN
Insert into AlertRanking(MetricInstanceID,GreenThreshold,RedThreshold,AlertTypeID,MaxThreshold,MinThreshold)
VALUES ((select id from #nonexistingTbl order by id OFFSET #i ROWS FETCH NEXT 1 ROWS ONLY), #greenThreshold, #redThreshold, #alertTypeID, #maxThreshold, #minThreshold)
set #id = (SELECT ID FROM AlertRanking
WHERE MetricInstanceID = (select id from #nonexistingTbl order by id OFFSET #i ROWS FETCH NEXT 1 ROWS ONLY)
AND GreenThreshold = #greenThreshold
AND RedThreshold = #redThreshold
AND AlertTypeID = #alertTypeID);
set #i = #i + 1;
END
Where #nonexistingTblCount is the total number of rows inside the table #nonexistingTbl. The #nonexistingTbl table is declared earlier and contains all the values we want to add to the table.
Instead of using a loop, you should be able to insert all of the records with a single statement.
INSERT INTO AlertRanking(MetricInstanceID,GreenThreshold,RedThreshold,AlertTypeID,MaxThreshold,MinThreshold)
SELECT id, #greenThreshold, #redThreshold, #alertTypeID, #maxThreshold, #minThreshold FROM #nonexistingTbl ORDER BY id
I have a table named WORD with the following columns
WORD_INDEX INT NOT NULL AUTO_INCREMENT,
CONTENT VARCHAR(255),
FREQUENCY INT
What I want to do is when I try to add a row to the table if a row with the same CONTENT exits, I want to increment the FREQUENCY by 1. Otherwise I want to add the row to the table. And then the WORD_INDEX in the newly inserted row or updated row must be returned.
I want to do this in H2 database from one query.
I have tried 'on duplicate key update', but this seems to be not working in H2.
PS- I can do this with 1st making a select query with CONTENT and if I get a empty result set, makeing insert query and otherwise making a update query. But as I have a very large number of words, I am trying to optimize the insert operation. So what I am trying to do is reducing the database interactions I am making.
Per your edited question .. you can achieve this using a stored procedure like below [A sample code]
DELIMITER $$
create procedure sp_insert_update_word(IN CONTENT_DATA VARCHAR(255),
IN FREQ INT, OUT Insert_Id INT)
as
begin
declare #rec_count int;
select #rec_count = count(*) from WORD where content = CONTENT_DATA;
IF(#rec_count > 0) THEN
UPDATE WORD SET FREQUENCY = FREQUENCY + 1 where CONTENT = CONTENT_DATA;
SELECT NULL INTO Insert_Id;
else
INSERT INTO WORD(CONTENT, FREQUENCY) VALUES(CONTENT_DATA, FREQ);
SELECT LAST_INSERT_ID() INTO Insert_Id;
END IF;
END$$
DELIMITER ;
Then call your procedure and select the returned inserted id like below
CALL sp_insert_update_word('some_content_data', 3, #Insert_Id);
SELECT #Insert_Id;
The above procedure code essentially just checking that, if the same content already exists then perform an UPDATE otherwise perform an INSERT. Finally return the newly generated auto increment ID if it's insert else return null.
First try to update frequency where content = "your submitted data here". If the affected row = 0 then insert a new row. You also might want make CONTENT unique considering it will always stored different data.
I have a base stored procedure simply returning a select from the database, like this:
CREATE PROCEDURE MyProcedure
AS
BEGIN
SELECT * FROM MyTable
END
GO
But now I need to execute some logic for every row of my select. According to the result I need to return or not this row. I would have my select statement running with a cursor, checking the rule and return or not the row. Something like this:
CREATE PROCEDURE MyProcedure
AS
BEGIN
DECLARE CURSOR_MYCURSOR FOR SELECT Id, Name FROM MyTable
OPEN CURSOR_MYCURSOR
FETCH NEXT FROM CURSOR_MYCURSOR INTO #OUTPUT1, #OUTPUT2
WHILE (##FETCH_STATUS=0)
BEGIN
IF (SOME_CHECK)
SELECT #OUTPUT1, #OUTPUT2
ELSE
--WILL RETURN SOMETHING ELSE
END
END
GO
The first problem is that everytime I do SELECT #OUTPUT1, #OUTPUT2 the rows are sent back as different result sets and not in a single table as I would need.
Sure, applying some logic to a row sounds like a "FUNCTION" job. But I can't use the result of the function to filter the results being selected. That is because when my check returns false I need to select something else to replace the faulty row. So, I need to return the faulty rows so I can be aware of them and replace by some other row.
The other problem with this method is that I would need to declare quite a few variables so that I can output them through the cursor iteration. And those variables would need to follow the data types for the original table attributes and somehow not getting out of sync if something changes on the original tables.
So, what is the best approach to return a single result set based on a criteria?
Thanks in advance.
I recommend use of cursors but easy solution to your question would be to use table variable or temp table
DECLARE #MyTable TABLE
(
ColumnOne VARCHAR(20)
,ColumnTwo VARCHAR(20)
)
CREATE TABLE #MyTable
(
ColumnOne VARCHAR(20)
,ColumnTwo VARCHAR(20)
)
than inside your cursors you can insert records that match your logic
INSERT INTO #MyTable VALUES (#Output1, #Output2)
INSERT INTO #MyTable VALUES (#Output1, #Output2)
after you done with cursor just select everything from table
SELECT * FROM #MyTable
SELECT * FROM #MyTable
I need to populate a column with the running count based on another column contents. The table is like this:
count seq_num
1 123-456-789
1 123-456-780
1 123-456-990
2 123-456-789
2 123-456-990
So, as the seq_num column changes, the counter resets to '1' and as the column repeats, the counter increments by 1.
This is using SQL2000, and the seq_num field is varchar.
Any ideas?
If you're inserting, you can use a subquery:
insert into
table (count, seq_num)
values
((select count(*)+1 from table where seq_num = #seq)
,#seq)
Otherwise, you'll need to have a date on there or some way of telling it how to determine what was first:
update table
set count =
(select count(*)+1 from table t2
where t2.seq_num = table.seq_num
and t2.insertdate < table.insertdate)
if you need to be able to continue updating this in the future, you might try this. It's a few steps but would fix it AND set it up for future use. (probably need to check my syntax - I mess with ORacle more now, so I may have mixed up some things - but the logic should work.)
first, create a table to contain the current counter level per sequence:
Create newTable (counter int, sequence varchar)
then, fill it with data like this:
insert into newTable
(select distinct 0 as Counter, sequence
from table)
This will put each sequence number in the table one time and the counter for each will be set at 0.
Then, create an update proc with TWO update statements and a bit of extra logic:
Create procedere counterUpdater(#sequence varchar) as
Declare l_counter as int;
select l_counter = counter
from newTable
where sequence = #sequence
--assuming you have a primary key in the table.
Declare #id int;
Select top 1 #id = id from table
where sequence = #sequence
and counter is null;
--update the table needing edits.
update table
set counter = l_counter + 1
where id = #id
--update the new table so you can keep track of which
--counter you are on
update newTable
set counter = l_counter + 1
where id = #id
Then run a proc to execute this proc for each record in your table.
Now you should have a "newTable" filled with the currently used counter for each record in the table. Set up your insert proc so that anytime a new record is created, if it is a sequence not already in the newTable, you add it with a count of 1 and you put a count of 1 in the main table. If the sequence DOES already exist, use the logic above (increment the count already in use the "newTable" and place that count as the counter value in the newTable and the mainTable.
Basically, this method decided to use memory in place of querying the existing table. It will become most beneficial if you have a large table with lots of repeated sequence numbers. If your sequence numbers only happen two or three times, you probably want to do a query instead when you update and then later insert:
First, to update:
--find out the counter value
Declare l_counter int
select l_counter = max(counter)
from table where sequence = #sequence
update table
set counter = l_counter + 1
where id = (select top 1 id from table where sequence = #sequence
and counter is null)
then run that for each record.
Then, when inserting new records:
Declare l_counter int
select l_counter = max(counter)
from table where sequence = #sequence
IsNull(l_counter, 0)
Insert into table
(counter, sequence) values (l_counter + 1, #sequence)
Again, I'm positive I've mixed-and-matched my syntaxes here, but the concepts should work. OF course, it's a "one at a time" approach instead of set based, so it might be a little inefficient, but it will work.