row number without using the ROW_NUMBER window function - sql-server

Question

Suppose you have a table with non-unique values such as this:
CREATE TABLE accounts ( fname VARCHAR(20), lname VARCHAR(20))
GO
INSERT accounts VALUES ('Fred', 'Flintstone')
INSERT accounts VALUES ('Fred', 'Flintstone')
INSERT accounts VALUES ('Fred', 'Flintstone')
SELECT * FROM accounts
GO
Now using a ROW_NUMBER function, you can get a unique incrementing row number.
select *, ROW_NUMBER() over(order by (select null)) as rn
from accounts
But how do we this without using a ROW_NUMBER function. I tried giving each row a unique ID using NEWID() and then counting the rows as given below but it did not work as it gives me a non-unique number which does not start with 1.
Note that I do not want to alter the table to add a new column.
;with cte as
(select *
from accounts as e
cross apply (select newid()) as a(id)
)
select *, (select count(*)+1 from cte as c1 where c.id > c1.id) as rn
from cte as c
order by rn
SQL Fiddle for toying around is http://sqlfiddle.com/#!18/c270f/3/0

Answer 1

The following demonstrates why your code fails, but does not provide an alternative to Row_Number().
A column, TopId, is added to the final select that should get the minimum value generated by NewId() and report it in every row. Instead, a new value is generated for each row.
-- Sample data.
declare #Samples as Table ( FName VarChar(20), LName VarChar(20) );
insert into #Samples ( FName, LName ) values
( 'Fred', 'Flintstone' ), ( 'Fred', 'Flintstone' ), ( 'Fred', 'Flintstone' );
select * from #Samples;
-- Cross apply NewId() in a CTE.
;with cte as
( select *
from #Samples as S
cross apply ( select NewId() ) as Ph( Id ) )
select *, ( select count(*) from cte as c1 where c1.Id >= c.Id ) as RN,
-- The following column should output the minimum Id value from the table for every row.
-- Instead, it generates a new unique identifier for each row.
( select top 1 id from cte order by id ) as TopId
from cte as c
order by RN;
The execution plan shows that the CTE is treated as a view that is being evaluated repeatedly, thus generating conflicting Id values.

Answer 2

How about this:
SELECT
src.*,
SUM(DummyVal) OVER(ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS RowId
FROM (
SELECT a.*, 1 AS DummyVal
FROM MyTable a
) src
It's still a window function, though, not sure if that matters.
Fiddle me this

Answer 3

You can create an function yourself to compute the row_number,
In this example, I had to calculate an index for a lesson within a course.
Window Function version:
SELECT *, ROW_NUMBER() OVER(PARTITION BY courseId) AS row_num FROM lessons;
I created helper-function, to compute the row_number without window function:
DELIMITER $$
CREATE FUNCTION getRowNumber (lessonId int, courseId int)
RETURNS int
DETERMINISTIC
BEGIN
DECLARE count int;
select count(l2.id) into count from lessons l2 where l2.courseId=courseId
and l2.id<=lessonId;
RETURN count;
END$$
DELIMITER ;
so, the final query is:
SELECT l.*, getRowNumber(l.id,l.courseId) as row_num FROM lessons l;
got the same result as the first query!

Answer 4

MySQL:
SELECT #rownum := #rownum + 1 AS rank, a.*
FROM accounts a,(SELECT #rownum := 0) r;
In ORACLE it would simply be
SELECT ROWNUM, a.*
FROM accounts a;
Both without window