Question

In MySQL I can do something like this:

SELECT @row := @row + 1 as num FROM
(select 0 union all select 1) t1,
(select 0 union all select 1) t2,
(select 0 union all select 1) t3,
(select @row := 0) as t4;

The output of which is:

num
1
2
3
4
5
6
7
8

I tried to do this in sql server, but met many road blocks:

First I tried this:

SELECT * FROM
(select 0 union all select 1) t1,
(select 0 union all select 1) t2,
(select 0 union all select 1) t3;

and received:

Msg 8155, Level 16, State 2, Line 7
No column name was specified for column 1 of 't1'.
Msg 8155, Level 16, State 2, Line 8
No column name was specified for column 1 of 't2'.
Msg 8155, Level 16, State 2, Line 9
No column name was specified for column 1 of 't3'.

So I did this:

SELECT * FROM
(select 0 as f union all select 1) t1,
(select 0 as f union all select 1) t2,
(select 0 as f union all select 1) t3;

1. Why do I have to specify a name for column 1 on the derived tables?

Next, I tried to setup a scalar, I guessed I had to do it this way:

DECLARE @row as int
SET @row = 0

I can do this:

SELECT @row = @row + 1

Which results in nothing back until I do SELECT @row which now shows a 1

I cannot do (as I was in MySQL at the start):

DECLARE @row as int
SET @row = 0

SELECT @row = @row + 1 as num FROM
(select 0 as f union all select 1) t1,
(select 0 as f union all select 1) t2,
(select 0 as f union all select 1) t3;

I get:

Msg 156, Level 15, State 1, Line 4
Incorrect syntax near the keyword 'as'.
Msg 102, Level 15, State 1, Line 5
Incorrect syntax near 't1'.
Msg 102, Level 15, State 1, Line 6
Incorrect syntax near 't2'.
Msg 102, Level 15, State 1, Line 7
Incorrect syntax near 't3'.

1. How do I mimic the behavior of the first query (from MySQL) in sql server?

Answer 1

Well, if you just want the row number, you could just use ROW_NUMBER() in TSQL;

SELECT ROW_NUMBER() OVER (ORDER BY t1.f) num FROM
  (SELECT 0 AS f UNION ALL SELECT 1) t1,
  (SELECT 0 AS f UNION ALL SELECT 1) t2,
  (SELECT 0 AS f UNION ALL SELECT 1) t3;

That will return the row number for each combination. ROW_NUMBER() requires an ORDER BY, so just order by the first convenient column.

SQLFiddle here.