Why use Select Top 100 Percent?

Question

I understand that prior to SQL Server 2005, you could \"trick\" SQL Server to allow use of an order by in a view definition, by also include TOP 100 PERCENT

Answer 1

The error says it all...

Msg 1033, Level 15, State 1, Procedure TestView, Line 5 The ORDER BY clause is invalid in views, inline functions, derived tables, subqueries, and common table expressions, unless TOP, OFFSET or FOR XML is also specified.

Don't use TOP 100 PERCENT, use TOP n, where N is a number

The TOP 100 PERCENT (for reasons I don't know) is ignored by SQL Server VIEW (post 2012 versions), but I think MS kept it for syntax reasons. TOP n is better and will work inside a view and sort it the way you want when a view is used initially, but be careful.

Answer 2

Just try this, it explains it pretty much itself. You can't create a view with an ORDER BY except if...

CREATE VIEW v_Test
         AS
           SELECT name
             FROM sysobjects
         ORDER BY name
        GO

Msg 1033, Level 15, State 1, Procedure TestView, Line 5 The ORDER BY clause is invalid in views, inline functions, derived tables, subqueries, and common table expressions, unless TOP, OFFSET or FOR XML is also specified.

Answer 3

Kindly try the below, Hope it will work for you.

      SELECT TOP
              ( SELECT COUNT(foo) 
                  From MyTable 
                 WHERE ISNUMERIC (foo) = 1) * 
                  FROM bar WITH(NOLOCK) 
              ORDER BY foo
                 WHERE CAST(foo AS int) > 100
               )

Answer 4

TOP (100) PERCENT is completely meaningless in recent versions of SQL Server, and it (along with the corresponding ORDER BY, in the case of a view definition or derived table) is ignored by the query processor.

You're correct that once upon a time, it could be used as a trick, but even then it wasn't reliable. Sadly, some of Microsoft's graphical tools put this meaningless clause in.

As for why this might appear in dynamic SQL, I have no idea. You're correct that there's no reason for it, and the result is the same without it (and again, in the case of a view definition or derived table, without both the TOP and ORDER BY clauses).

Answer 5

It was used for "intermediate materialization (Google search)"

Good article: Adam Machanic: Exploring the secrets of intermediate materialization

He even raised an MS Connect so it can be done in a cleaner fashion

My view is "not inherently bad", but don't use it unless 100% sure. The problem is, it works only at the time you do it and probably not later (patch level, schema, index, row counts etc)...

Worked example

This may fail because you don't know in which order things are evaluated

SELECT foo From MyTable WHERE ISNUMERIC (foo) = 1 AND CAST(foo AS int) > 100

And this may also fail because

SELECT foo
FROM
    (SELECT foo From MyTable WHERE ISNUMERIC (foo) = 1) bar
WHERE
    CAST(foo AS int) > 100

However, this did not in SQL Server 2000. The inner query is evaluated and spooled:

SELECT foo
FROM
    (SELECT TOP 100 PERCENT foo From MyTable WHERE ISNUMERIC (foo) = 1 ORDER BY foo) bar
WHERE
    CAST(foo AS int) > 100

Note, this still works in SQL Server 2005

SELECT TOP 2000000000 ... ORDER BY...

Answer 6

I would suppose that you can use a variable in the result, but aside from getting the ORDER BY piece in a view, you will not see a benefit by implicitly stating "TOP 100 PERCENT":

declare @t int
set @t=100
select top (@t) percent * from tableOf