Question

I have a table T (structure below) which initially contains all-NULL values in an integer order column:

col1  varchar(30),
col2  varchar(30),
order int NULL

I also have a way to order the “colN” columns, e.g.

SELECT * FROM T ORDER BY some_expression_involving_col1_and_col2

What’s the best way to assign – IN SQL – numeric order values 1-N to the order table, so that the order values match the order of rows returned by the above ORDER BY?

In other words, I would like a single query (Sybase SQL syntax so no Oracle’s rowcount) which assigns order values so that SELECT * FROM T ORDER BY order returns 100% same order of rows as the query above.

The query does NOT necessarily need to update the table T in place, I’m OK with creating a copy of the table T2 if that’ll make the query simpler.

NOTE1: A solution must be real query or a set of queries, not involving a loop or a cursor.

NOTE2: Assume that the data is uniquely orderable according to the order by above – no need to worry about situation when 2 rows can be assigned the same order at random.

NOTE3: I would prefer a generic solution, but if you wish a specific example of ordering expression, let’s say:

SELECT * FROM T 
ORDER BY CASE WHEN col1="" THEN "AAAAAA" ELSE col1 END, ISNULL(col2, "ZZZ")

Answer 1

I used as an example the roysched table in pubs2. I added a column id (int NULL) and used as an ordering logic the following:

substring(title_id,3,4) + right(replicate('0',5) + convert(varchar,lorange),5)

Then I created (and updated) a view. To avoid duplicating, I used strings

Declare @strSql varchar(1000), @strOrder varchar(256)
set @strOrder = "substring(title_id,3,4) + right(replicate('0',5) + convert(varchar,lorange),5)"

set @strSql = "create view my_roysched (id,my_order)
as 
select id, (select count(*) from (select " + @strOrder + " as my_order from roysched) BETA 
              where BETA.my_order <= ALPHA.my_order) as my_id 
      from (select id," + @strOrder + " as my_order from roysched ) as ALPHA 

update my_roysched 
set id = my_order

drop view my_roysched"

exec (@strSql)

Now if you give

select * from roysched
order by substring(title_id,3,4) + right(replicate('0',5) + convert(varchar,lorange),5)

you will see that id match the order of rows returned by the above order by