Add a row number to result set of a SQL query

I have a simple select statement. I want to add a temporary column which will number the rows in my result set. I tried this -

declare @num int set @num = 0; select t.A, t.B, t.C, (@count + 1) as number from tableZ as t 

It assigns the 1 to all rows. I tried @count = @count + 1 and it did not work. How do I do this thing in a simple manner ?

thanks.

2 Answers

SELECT t.A, t.B, t.C, ROW_NUMBER() OVER (ORDER BY (SELECT 1)) AS number FROM tableZ AS t 

See working example at SQLFiddle

Of course, you may want to define the row-numbering order – if so, just swap OVER (ORDER BY (SELECT 1)) for, e.g., OVER (ORDER BY t.C), like in a normal ORDER BY clause.

The typical pattern would be as follows, but you need to actually define how the ordering should be applied (since a table is, by definition, an unordered bag of rows). One way to do that if you don't care about a specific order otherwise is to use the leading key(s) of a covering index, the leading key(s) of the clustered index, or the columns in any group by / order by clauses. In this case I'll assume A is the single-column clustering key for t:

SELECT t.A, t.B, t.C, number = ROW_NUMBER() OVER (ORDER BY t.A) FROM dbo.tableZ AS t ORDER BY t.A; 

If you truly don't care about order, you can generate arbitrary/nondeterministic row numbering using:

ROW_NUMBER() OVER (ORDER BY @@SPID) -- or for serial plans ROW_NUMBER() OVER (ORDER BY @@TRANCOUNT) 

Little tricks I picked up from Paul White in this article (see "Paul's Solution").

Not sure what the variables in your question are supposed to represent (they don't match).