Order By Issue with MySQL vs SQL Server - mysql

Question

I have one SQL query in SQL Server like this
SELECT
CASE WHEN ROW_NUMBER() OVER(PARTITION BY _no ORDER BY _no asc) = 1 THEN
_no ELSE '' END
as row_no,
_no,
_name,
r._names
FROM
(
SELECT '1' as _no, 'vikas' as _name UNION ALL
SELECT '1', 'kratika' UNION ALL
SELECT '2', 'vikas' UNION ALL
SELECT '1', 'kratika kastwar'
) t
INNER JOIN
(
SELECT '1' as _nos, 'One' as _names UNION ALL
SELECT '2', 'two'
) r
ON r._nos = t._no
ORDER BY _no
Output:
row_no _no _name _names
------ ---- --------------- ------
1 1 kratika One
1 kratika kastwar One
1 vikas One
2 2 vikas two
And the same I am doing in MySQL like this
SELECT
CASE WHEN _no = #i THEN '' ELSE #i := _no END
as row_no,
_no,
_name,
r._names
FROM
(
SELECT '1' as _no, 'vikas' as _name UNION ALL
SELECT '1', 'kratika' UNION ALL
SELECT '2', 'vikas' UNION ALL
SELECT '1', 'kratika kastwar'
) t
INNER JOIN
(
SELECT '1' as _nos, 'One' as _names UNION ALL
SELECT '2', 'two'
) r
ON r._nos = t._no
,
(SELECT #i := '') temp
ORDER BY _no
Output :
1 1 vikas One
1 kratika One
1 1 kratika kastwar One
2 2 vikas two
But I am expecting output in MySQL like this
1 1 kratika One
1 kratika kastwar One
1 vikas One
2 2 vikas two
I don't want to use query like this in MySQL as desc here MYSQL Order By W/Count
SELECT
CASE WHEN _no = #i THEN '' ELSE #i := _no END
as row_no,
_no,
_name,
_names
FROM
(SELECT
*
FROM
(
SELECT '1' as _no, 'vikas' as _name UNION ALL
SELECT '1', 'kratika' UNION ALL
SELECT '2', 'vikas' UNION ALL
SELECT '1', 'kratika kastwar'
) t
INNER JOIN
(
SELECT '1' as _nos, 'One' as _names UNION ALL
SELECT '2', 'two'
) r
ON r._nos = t._no
,
(SELECT #i := '') temp
ORDER BY _no) t
How I can achieve the same in MySQL, query performance is major parameter

Answer 1

I think what's happening here is that MySQL is constructing the resultset and then going through an extra step to order it according to the ORDER BY clause. Since the 'kratika kastwar' row comes after the row where _no is 2, you get the unexpected output.
The solution, I guess, would be to put the basic SELECT (without the special user-variable shenanigans) in a subquery in the FROM clause, applying the ORDER BY clause to the subquery. Then do the user-variable work in the outer query. That way the ordering has already happened.
Edit: I see that you said you don't want to do this. I don't think you have a choice, unless you can find a way to get MySQL to not do the ORDER BY by performing a filesort step on the computed results (very unlikely).

Answer 2

SELECT
CASE WHEN _no = #i THEN '' ELSE #i := _no END
as row_no,
_no,
_name,
_names
FROM
(SELECT
*
FROM
(
SELECT '1' as _no, 'vikas' as _name UNION ALL
SELECT '1', 'kratika' UNION ALL
SELECT '2', 'vikas' UNION ALL
SELECT '1', 'kratika kastwar'
) t
INNER JOIN
(
SELECT '1' as _nos, 'One' as _names UNION ALL
SELECT '2', 'two'
) r
ON r._nos = t._no
,
(SELECT #i := '')