I want to use CTE with while loop. Is it possible
my code:
; with myCTE(a,b)
(
select .,. from abc
)
while exist (select * from mycet) -- causing issue
Please suggest some solution.
Regards,
Anuprita
No, the documentation states:
A CTE must be followed by a single SELECT, INSERT, UPDATE, or DELETE
statement that references some or all the CTE columns.
But you should use a set based approach instead of loops anyway. Apart from that, it is not clear what your query should return.
Related
How do I remove duplicates in the following case in T-SQL?
I have a table with a column Code of type varchar(max).
It contains column value like truck/rail/truck/rail. I need the cell value to be truck/rail.
Other possibility is truck/rail/ship/truck need to be truck/rail/ship.
By using table valued function.
Thanks.
You can use String_Split along with String_agg to remove the duplicates.
DECLARE #t table(id int, val varchar(max))
insert into #t values(1,'truck/rail/truck/rail'), (2,'truck/rail/ship/truck')
SELECT t.id,STRING_AGG(splitval,'/') as newval FROM #t as t
cross apply (
SELECT distinct value from string_split(t.val,'/')) as ca(splitval)
group by t.id
id
newval
1
rail/truck
2
rail/ship/truck
Note1: String_Split, does not guarantee order. So, your concatenated results might be in different order from the original list, after duplicates removal. If you want to preserve the order, then we have to go for different solution using xml nodes or json array.
Note2: String_Split was introduced in SQL Server 2016. String_agg was introduced in SQL Server 2017. So, if you are using versions before that, you have to go for recursive CTE and CHARINDEX based solution.
If you know that the error exists, then just do an UPDATE where you replace the truck/rail/truck/rail with truck/rail using the REPLACE(Code,'truck/rail/truck/rail',truck/rail).
The same goes for your truck/rail/ship/truck issue.
If you need automatic detection and correction to be done, that's a whole 'nuther story but could still be done using nested REPLACES. Detection of the issue is the hard part. Personally, I'd be having a talk with the people that are providing the data.
I'm using the following code:
SELECT * FROM table
WHERE Col IN (123,123,222,....)
However, if I put more than ~3000 numbers in the IN clause, SQL throws an error.
Does anyone know if there's a size limit or anything similar?!!
Depending on the database engine you are using, there can be limits on the length of an instruction.
SQL Server has a very large limit:
http://msdn.microsoft.com/en-us/library/ms143432.aspx
ORACLE has a very easy to reach limit on the other side.
So, for large IN clauses, it's better to create a temp table, insert the values and do a JOIN. It works faster also.
There is a limit, but you can split your values into separate blocks of in()
Select *
From table
Where Col IN (123,123,222,....)
or Col IN (456,878,888,....)
Parameterize the query and pass the ids in using a Table Valued Parameter.
For example, define the following type:
CREATE TYPE IdTable AS TABLE (Id INT NOT NULL PRIMARY KEY)
Along with the following stored procedure:
CREATE PROCEDURE sp__Procedure_Name
#OrderIDs IdTable READONLY,
AS
SELECT *
FROM table
WHERE Col IN (SELECT Id FROM #OrderIDs)
Why not do a where IN a sub-select...
Pre-query into a temp table or something...
CREATE TABLE SomeTempTable AS
SELECT YourColumn
FROM SomeTable
WHERE UserPickedMultipleRecordsFromSomeListOrSomething
then...
SELECT * FROM OtherTable
WHERE YourColumn IN ( SELECT YourColumn FROM SomeTempTable )
Depending on your version, use a table valued parameter in 2008, or some approach described here:
Arrays and Lists in SQL Server 2005
For MS SQL 2016, passing ints into the in, it looks like it can handle close to 38,000 records.
select * from user where userId in (1,2,3,etc)
I solved this by simply using ranges
WHERE Col >= 123 AND Col <= 10000
then removed unwanted records in the specified range by looping in the application code. It worked well for me because I was looping the record anyway and ignoring couple of thousand records didn't make any difference.
Of course, this is not a universal solution but it could work for situation if most values within min and max are required.
You did not specify the database engine in question; in Oracle, an option is to use tuples like this:
SELECT * FROM table
WHERE (Col, 1) IN ((123,1),(123,1),(222,1),....)
This ugly hack only works in Oracle SQL, see https://asktom.oracle.com/pls/asktom/asktom.search?tag=limit-and-conversion-very-long-in-list-where-x-in#9538075800346844400
However, a much better option is to use stored procedures and pass the values as an array.
You can use tuples like this:
SELECT * FROM table
WHERE (Col, 1) IN ((123,1),(123,1),(222,1),....)
There are no restrictions on number of these. It compares pairs.
I need to re-assign all SortID's, starting from 1 until MAX (SortID) from a subset of records of table Beleg, using SQL-92, after one of the SortID's has changed (for example from 444 to 444.1). I have tried several ways (for example SET #a:=0; UPDATE table SET field=#a:=#a+1 WHERE whatever='whatever' ORDER BY field2), but it didn't work, as these solutions all need a special kind of SQL, like SQLServer or Oracle, etc.
The SQL that I use is SQL-92, implemented in FileMaker (INSERT and UPDATE are available, though, but nothing fancy).
Thanks for any hint!
Gary
From what I know, SQL-92 is a standard and not a language. So you can say you are using T-SQL, which is mostly SQL-92 compliant, but you can't say I program SQL Server in SQL-92. The same applies to FileMaker.
I suppose you are trying to update your table through ODBC? The Update statement looks OK, but there are no variables if FileMaker SQL (and I am not sure using a variable inside query will give you result you expect, I think you will set SortId in every row to 1). You are thinking about doing something like Window functions with row() in TSQL, but I do not think this functionality is available.
The easiest solution is to use FileMaker, resetting the numbering for a column is really a trivial task which takes seconds. Do you need help with this?
Edit:
I was referring to TSQL functions rank() and row_number(), there is no row() function in TSQL
I finally got the answer from Ziggy Crueltyfree Zeitgeister on the Database Administrators copy of my question.
He suggested to break this down into multiple steps using a temporary table to store the results:
CREATE TABLE sorting (sid numeric(10,10), rn int);
INSERT INTO sorting (sid, rn)
SELECT SortID, RecordNumber FROM Beleg
WHERE Year ( Valuta ) = 2016
AND Ursprungskonto = 1210
ORDER BY SortID;
UPDATE Beleg SET SortID = (SELECT rn FROM sorting WHERE sid=Beleg.SortID)
WHERE Year ( Valuta ) = 2016
AND Ursprungskonto = 1210;
DROP TABLE sorting;
Of course! I just keep the table definition in Filemaker (let the type coercion be done by Filemaker this way), and filling and deleting from it with my function: RenumberSortID ().
I've got a question which occurs when I was using the WITH-clause in one of my script. The question is easy to pointed out I wanna use the CTE alias multiple times instead of only in outer query and there is crux.
For instance:
-- Define the CTE expression
WITH cte_test (domain1, domain2, [...])
AS
-- CTE query
(
SELECT domain1, domain2, [...]
FROM table
)
-- Outer query
SELECT * FROM cte_test
-- Now I wanna use the CTE expression another time
INSERT INTO sometable ([...]) SELECT [...] FROM cte_test
The last row will lead to the following error because it's outside the outer query:
Msg 208, Level 16, State 1, Line 12 Invalid object name 'cte_test'.
Is there a way to use the CTE multiple times resp. make it persistent? My current solution is to create a temp table where I store the result of the CTE and use this temp table for any further statements.
-- CTE
[...]
-- Create a temp table after the CTE block
DECLARE #tmp TABLE (domain1 DATATYPE, domain2 DATATYPE, [...])
INSERT INTO #tmp (domain1, domain2, [...]) SELECT domain1, domain2, [...] FROM cte_test
-- Any further DML statements
SELECT * FROM #tmp
INSERT INTO sometable ([...]) SELECT [...] FROM #tmp
[...]
Frankly, I don't like this solution. Does anyone else have a best practice for this problem?
Thanks in advance!
A CommonTableExpression doesn't persist data in any way. It's basically just a way of creating a sub-query in advance of the main query itself.
This makes it much more like an in-line view than a normal sub-query would be. Because you can reference it repeatedly in one query, rather than having to type it again and again.
But it is still just treated as a view, expanded into the queries that reference it, macro like. No persisting of data at all.
This, unfortunately for you, means that you must do the persistance yourself.
If you want the CTE's logic to be persisted, you don't want an in-line view, you just want a view.
If you want the CTE's result set to be persisted, you need a temp table type of solution, such as the one you do not like.
A CTE is only in scope for the SQL statement it belongs to. If you need to reuse its data in a subsequent statement, you need a temporary table or table variable to store the data in. In your example, unless you're implementing a recursive CTE I don't see that the CTE is needed at all - you can store its contents straight in a temporary table/table variable and reuse it as much as you want.
Also note that your DELETE statement would attempt to delete from the underlying table, unlike if you'd placed the results into a temporary table/table variable.
I want to write a update SQL statement, but one conidtion of this statement is the result from a select SQL statement, and I also want to return the result of the select SQL statement.
Like this: update ... set ... where id = (select id from ...)
I want to return the value of id back.
Does anybody know how should I do this?
Thanks in advance!
I don't believe that's possible in one statement. Update then query (select) the new value, or query the value first, and then submit an update.
Alternative would be a stored procedure on the database, which executes the multiple queries and returns the result for you.
This is not possible in all Java database frameworks that I know. Probably you need to separate your query and update in Java.
I don't see any problem in using a subselect in a WHERE clause of an update statement.
For the second request, getting back the value of id, I know this is possible in DB2, and maybe others implement that syntax too:
SELECT id FROM FINAL TABLE (
update ... set ... where id = (select id from ...)
)
This works also for INSERT and DELETE statements. (See the documentation.)
Update statements won't return the updated datasets. The select in that case would be a subselect that isn't directly accessible.
You'd thus have to use at least two queries:
select the ids you want
call the update query passing the previously selected ids as a parameter