SQL Server How do I write LINQ's .Skip(1000).Take(100) in pure SQL?

qmelpv7a  于 2023-08-02  发布在  其他
关注(0)|答案(7)|浏览(100)

What is the SQL equivalent of the .Skip() method in LINQ?

For example: I would like to select rows 1000-1100 from a specific database table.

Is this possible with just SQL? Or do I need to select the entire table, then find the rows in memory? I'd ideally like to avoid this, if possible, since the table can be quite large.

z9ju0rcb

z9ju0rcb1#

SQL Server 2012 and above have added this syntax:

SELECT *
FROM Sales.SalesOrderHeader 
ORDER BY OrderDate
OFFSET (@Skip) ROWS FETCH NEXT (@Take) ROWS ONLY
gfttwv5a

gfttwv5a2#

In SQL Server 2005 and above you can use ROW_NUMBER function. eg.

USE AdventureWorks;
GO
WITH OrderedOrders AS
(
    SELECT SalesOrderID, OrderDate,
    ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
    FROM Sales.SalesOrderHeader 
) 
SELECT * 
FROM OrderedOrders 
WHERE RowNumber BETWEEN 51 AND 60; --BETWEEN is inclusive
euoag5mw

euoag5mw3#

LINQ to SQL does this by using a ROW_NUMBER windowing function:

SELECT a,b,c FROM 
   (SELECT a,b,c, ROW_NUMBER() OVER (ORDER BY ...) as row_number
    FROM Table) t0
   WHERE to.row_number BETWEEN 1000 and 1100;

This works, but the need to manufacture the row_number from the ORDER BY may result in your query being sorted on the server side and cause performance problems. Even when an index can satisfy the ORDER BY requirement, the query still has to count 1000 rows before startting to return results. All too often developers forget this and just throw a pagination control over a 5 mil rows table and wonder why the first page is returned so much faster than the last one...

None the less, using ROW_NUMBER() is probably the best balance between ease of use and good performance, provided you make sure you avoid the sort (the ORDER BY condition can be satisified by an index).

vdgimpew

vdgimpew4#

Try this one:

select * from [Table-Name] order by [Column-Name] 
offset [Skip-Count] rows
FETCH NEXT [Take-Count] rows only

Example:

select * from Personals order by Id
offset 10 rows            --------->Skip 10
FETCH NEXT 15 rows only   --------->Take 15
rwqw0loc

rwqw0loc5#

Do this:

Run .Skip(1000).Take(100) on a LINQ to SQL datacontext and look at the SQL output. It will generate a SQL statement for you that does what you're describing.

It won't be as elegant but it gets the job done.

b4qexyjb

b4qexyjb6#

No, but you could emulate MySQL's LIMIT clause (Stack Overflow link) to achieve the same result.

vwhgwdsa

vwhgwdsa7#

Linqpad also has a SQL view you could use to get the SQL:

相关问题