I have a parameter in my stored procedure that specifies number of rows to select. (Possible values: 0-100. 0 Means Select All rows)
For example #Rows = 5;
Then I can do this:
Insert into #MyTableVar
Select Top(#Rows) *
from myTable
Now, as I said before if 0 is supplied I need to return all rows.
This is a pseudo-code of what I need:
if (#Rows=0) then select * else select top(#Rows) *
I found out that there's SET ROWCOUNT that accepts 0 to return ALL rows, but I need to do an insert into a table variable which is not supported by ROWCOUNT.
Is it possible to achieve this without dynamic sql?
(I understand that I can write a simple if else statement and duplicate query, but I have pretty complex queries and there are lots fo them, I just want to avoid code duplication)
One way is to just put a big number in:
set #Rows = 5;
declare #RowsToUse = (case when #Rows = 0 then 1000000000 else #Rows end);
select top(#RowsToUse) * from myTable
First of all, you are missing the ORDER BY clause, since you are using TOP. You could do this:
SET #Rows = 5;
WITH CTE AS
(
SELECT *,
RN = ROW_NUMBER() OVER(ORDER BY Id) --put the right order here
FROM myTable
)
INSERT INTO #MyTableVar
SELECT YourColumns
FROM CTE
WHERE RN <= #Rows OR #Rows = 0
Related
I won't be surprised if SQL just doesn't work this way at all, but:
If we run two SELECT statements in a query, we get a split "Results" pane. I'm wondering if I can add variables to a list, and then have the number of result pane splits match the length of that list.
If I were to mix languages:
id_list = [26275, 54374, 84567]
for i in id_list:
SELECT * FROM table WHERE id = i
I'm just trying to easily compare results of a query while keeping distinct groups, with a changing number of variables. Since loops never seem to be the answer in SQL, I'd be just as happy inserting something like a blank line or horizontal rule, etc. Not sure if that's possible either though...
There is no concept of "lists" (as a separate data structure) in T-SQL. Does this do what you want?
SELECT *
FROM table
WHERE id IN (26275, 54374, 84567);
declare #i int = 0;
declare #Id int;
declare #Ids table (Id int);
insert #Ids select Id from (values (26275), (54374), (84567)) t(Id);
-- OR: insert #Ids select * from string_split('26275, 54374, 84567', ',');
declare #Count int = (select count(*) from #Ids);
while #i < #Count
begin
select #Id = Id, #i = #i + 1
from #Ids order by Id
offset #i rows fetch next 1 rows only;
select * from dbo.MyTable where Id = #Id;
end
You can use UNION ALL:
SELECT * FROM table WHERE id = 26275
UNION ALL
SELECT * FROM table WHERE id = 54374
UNION ALL
SELECT * FROM table WHERE id = 84567
A local variable #V_COUNT INT. If the variable #V_COUNT is '0'(zero) the return all the records from table otherwise return the number of {#V_COUNT} records from table. For example if #V_COUNT = 50, return TOP 50 records. If #V_COUNT is 0 then return TOP 100 PERCENT records. Can we achieve this in a single query?
Sample query :
DECLARE #V_COUNT INT = 0
SELECT TOP (CASE WHEN #V_COUNT > 0 THEN #V_COUNT ELSE 100 PERCENT END) *
FROM MY_TABLE
ORDER BY COL1
Incorrect syntax near the keyword 'percent'
A better solution would be to not use TOP at all - but ROWCOUNT instead:
SET ROWCOUNT stops processing after the specified number of rows.
...
To return all rows, set ROWCOUNT to 0.
Please note that ROWCOUNT is recommended to use only with select statements -
Important
Using SET ROWCOUNT will not affect DELETE, INSERT, and UPDATE statements in a future release of SQL Server. Avoid using SET ROWCOUNT with DELETE, INSERT, and UPDATE statements in new development work, and plan to modify applications that currently use it. For a similar behavior, use the TOP syntax.
DECLARE #V_COUNT INT = 0
SET ROWCOUNT #V_COUNT -- 0 means return all rows...
SELECT *
FROM MY_TABLE
ORDER BY COL1
SET ROWCOUNT 0 -- Avoid side effects...
This will eliminate the need to know how many rows there are in the table
Be sure to re-set the ROWCOUNT back to 0 after the query, to avoid side effects (Good point by Shnugo in the comments).
Instead of 100 percent you can write some very big number, which will surely be bigger than possible number of rows returned by the query, eg. max int which is 2147483647.
You can do something like:
DECLARE #V_COUNT INT = 0
SELECT TOP (CASE WHEN #V_COUNT > 0 THEN #V_COUNT ELSE (SELECT COUNT(1) FROM MY_TABLE) END) *
FROM MY_TABLE
DECLARE #V_COUNT int = 3
select *
from
MY_TABLE
ORDER BY
Service_Id asc
offset case when #V_COUNT >0 then ((select count(*) from MY_TABLE)- #V_COUNT) else #V_COUNT end rows
SET ROWCOUNT forces you into procedural logic. Furthermore, you'll have to provide an absolute number. PERCENT would need some kind of computation...
You might try this:
DECLARE #Percent FLOAT = 50;
SELECT TOP (SELECT CAST(CAST((SELECT COUNT(*) FROM sys.objects) AS FLOAT)/100.0 * CASE WHEN #Percent=0 THEN 100 ELSE #Percent END +1 AS INT)) o.*
FROM sys.objects o
ORDER BY o.[name];
This looks a bit clumsy, but the computation will be done once within microseconds...
I want to have a variable for selecting top rows. I can select top rows based on a variable. However I want to select all rows if the variable is not supplied.
Currently I'm using this query:
DECLARE #TOPCOUNT int;
SET #TOPCOUNT=10;
SELECT TOP(#TOPCOUNT) * FROM TABLE1
Update:
The original query is very lengthy and complex, so I don't to rewrite the entire query without top count in else clause.
I don't want to use dynamic query because of its repercussions.
Something like this:
DECLARE #TOPCOUNT int;
--SET #TOPCOUNT=10;
IF #TOPCOUNT IS NULL
SELECT * FROM TABLE1
ELSE
SELECT TOP(#TOPCOUNT) * FROM TABLE1
Added after above UPDATE - if this is a parameter of a Stored Procedure then just provide a default for #TOPCOUNT:
#TOPCOUNT INT = 2147483647 --max size of INT
Something like this will help. Just init your #TOPCOUNT with -1 if you want all rows.
IF #TOPCOUNT = -1 BEGIN
SELECT * FROM TABLE1
END
ELSE BEGIN
SELECT TOP(#TOPCOUNT) * FROM TABLE1
END
IF #TOPCOUNT IS NULL SET #TOPCOUNT=2147483647
I want to create a stored procedure which takes integer values as a #top from me so that I can use it in my query, but it's not allowing me to set value of top dynamically.
select top #top * from (select url,
count(1) as shared from tblshared
group by url, uniqid having
uniqid = #uniqid) as sha order by
shared desc
I want to retrieve top n records from table so I want to pass the value of n in stored procedure and it will return me that number of top records.
Note: I don't want to use exec.
Thanks.
That will work fine if you wrap #top in brackets
select top (#top) *
from (
select url, count(1) as shared
from tblshared
group by url, uniqid
having uniqid=#uniqid) as sha
order by shared desc
You can use ROW_NUMBER() isntead of top
with t1 as(
select url,row_number() over(
partition by url, uniqid order by url, uniqid desc) as shared
from tblshared
where uniqid = #uniqid )
select * from t1 where shared < #top
REF
You could use SET ROWCOUNT:
SET ROWCOUNT #top
SELECT ...
SET ROWCOUNT 0
declare #v1 int
set #v1 = 25
set rowcount #v1
select * from MyTable Order by DateColumn
set rowcount 0
I have a query that returns a large number of heavy rows.
When I transform this rows in a list of CustomObject I have a big memory peak, and this transformation is made by a custom dotnet framework that I can't modify.
I need to retrieve a less number of rows to do "the transform" in two passes and then avoid the memory peak.
How can I split the result of a query by half? I need to do it in DB layer. I thing to do a "Top count(*)/2" but how to get the other half?
Thank you!
If you have identity field in the table, select first even ids, then odd ones.
select * from Table where Id % 2 = 0
select * from Table where Id % 2 = 1
You should have roughly 50% rows in each set.
Here is another way to do it from(http://www.tek-tips.com/viewthread.cfm?qid=1280248&page=5). I think it's more efficient:
Declare #Rows Int
Declare #TopRows Int
Declare #BottomRows Int
Select #Rows = Count(*) From TableName
If #Rows % 2 = 1
Begin
Set #TopRows = #Rows / 2
Set #BottomRows = #TopRows + 1
End
Else
Begin
Set #TopRows = #Rows / 2
Set #BottomRows = #TopRows
End
Set RowCount #TopRows
Select * From TableName Order By DisplayOrder
Set RowCount #BottomRows
Select * From TableNameOrder By DisplayOrderDESC
--- old answer below ---
Is this a stored procedure call or dynamic sql? Can you use temp tables?
if so, something like this would work
select row_number() OVER(order by yourorderfield) as rowNumber, *
INTO #tmp
FROM dbo.yourtable
declare #rowCount int
SELECT #rowCount = count(1) from #tmp
SELECT * from #tmp where rowNumber <= #rowCount / 2
SELECT * from #tmp where rowNumber > #rowCount / 2
DROP TABLE #tmp
SELECT TOP 50 PERCENT WITH TIES ... ORDER BY SomeThing
then
SELECT TOP 50 PERCENT ... ORDER BY SomeThing DESC
However, unless you snapshot the data first, a row in the middle may slip through or be processed twice
I don't think you should do that in SQL, unless you will always have a possibility to have the same record 2 times.
I would do it in an "software" programming language, not SQL. Java, .NET, C++, etc...