SQL Server select queries union all and limit - sql

Question

I have a lot of problems to migrate queries from Mysql to SQL Server. I have this query that is a bit complicated but in mysql it works fine.
I have a select from a table union all to a select from another table not equals and a limit to paginate the results because the rows returned are a lot. When I tried to migrate to SQL Server, the selects with the union work fine. When I read how to implement a limit in T-SQL, in stackoverflow and another pages I learned how to do but when I try to apply it to my query it does not run and SQL Server returns an error.
The query without limit is the following (this query works well):
SELECT
'false' AS historico,
'' AS tabla,
a.nombre,
a.apellido1,
a.apellido2
FROM
persons a
WHERE
a.eliminado = 'N'
AND (idconv = 30)
UNION ALL
SELECT
'true' AS historico,
b.tabla,
b.nombre,
b.apellido1,
b.apellido2
FROM
persons_hist b
WHERE
b.eliminado = 'N'
AND (tabla = '1955')
ORDER BY
apellido1 ASC
but when I try to add "pagination" for example 10 rows starting in 0 this query returns me 18 rows 9 rows from the first table and 9 rows from the second table, but I have to paginate for example 10 rows from the union of 2 tables.
;WITH Results_CTE AS
(
select
ROW_NUMBER() OVER (ORDER BY apellido1 asc ) AS RowNum ,
'false' as historico,
'' as tabla,
a.nombre, a.apellido1, a.apellido2
from
persons a
where
a.eliminado = 'N' and (idconv = 30)
union all
select
ROW_NUMBER() OVER (ORDER BY apellido1 asc ) AS RowNum ,
'true' as historico,
b.tabla, b.nombre, b.apellido1, b.apellido2
from
persons_hist b
where
b.eliminado = 'N' and (tabla = '1997')
)
SELECT *
FROM Results_CTE
WHERE RowNum >= 0
AND RowNum < 0 + 10
Can somebody please help me?

Answer 1

one problem is that SQL SERVER row_number starts at 1 - you do not get a 0, so you have asked for 0 - 9 which will be 9 rows/
your other problem seems to be that row_number is calculated separately for each part of the UNION (which is logical for it to do so) - try calculating row number in a 2nd CTE
try
;WITH Results_CTE1 AS
(
select 'false' as historico,'' as tabla,a.nombre,a.apellido1,a.apellido2 from persons a where a.eliminado = 'N' and ( idconv = 30 )
union all
select 'true' as historico,b.tabla,b.nombre,b.apellido1,b.apellido2 from persons_hist b
where b.eliminado = 'N' and ( tabla = '1997' )
),
Results_CTE AS
(
SELECT *,ROW_NUMBER() OVER (ORDER BY apellido1 asc ) AS RowNum FROM Results_CTE1
)
SELECT *
FROM Results_CTE
WHERE RowNum BETWEEN 1 AND 10

Answer 2

You have 2 separate rownumbers in here. Try this:
WITH Results_CTE AS
(
'false' as historico,'' as tabla,a.nombre,a.apellido1,a.apellido2 from persons a where a.eliminado = 'N' and ( idconv = 30 )
union all
'true' as historico,b.tabla,b.nombre,b.apellido1,b.apellido2 from persons_hist b
where b.eliminado = 'N' and ( tabla = '1997' )
)
select *
from
(
select CTE1.*, row_number() over (order by apellido1 ) as RowNum
from Results_CTE
)
where RowNum <=10