increment a variable foreach record - sql

Question

I have this query :
#create table #tmp_table( n_progressive int , name char(10),
id_numeric(11,0) )
declare #i int = 0 declare #c int declare n_progressive int = 0
declare #var_table table ( name char(10), id_number numeric(11,0) )
insert into #var_table( name, id_number ) select name,id_number from MainTable
select #c= count (*) from #var_table
while(#i<#c) begin set #n_progressive = #n_progressive + 1
insert into #Tmptable( n_progressive , name , id_numeric ) select #n_progressive ,name,id_numeric from #var_table
end
The records in var_table are 4. and for each record I want the n_progressive to be incremented +1.
The result of the query above is this :
+--------------+----------+------------+
|n_progressive | name | numeric_id |
+--------------+----------+------------+
|1 | RM1 | 1 |
|1 | RM2 | 2 |
|1 | RM3 | 3 |
|1 | RM4 | 4 |
|2 | RM1 | 1 |
|2 | RM2 | 2 |
|2 | RM3 | 3 |
|2 | RM4 | 4 |
|3 | RM1 | 1 |
|3 | RM2 | 2 |
|3 | RM3 | 3 |
|3 | RM4 | 4 |
|4 | RM1 | 1 |
|4 | RM2 | 2 |
|4 | RM3 | 3 |
|4 | RM4 | 4 |
+--------------+----------+------------+
What I want is this :
+---------------+----------+-------------+
|n_progressive | name | numeric_id |
+---------------+----------+-------------+
|1 | RM1 | 1 |
|2 | RM2 | 2 |
|3 | RM3 | 3 |
|4 | RM4 | 4 |
+---------------+----------+-------------+
I don't want to use Cursors.

Answer 1

You are selecting all the records from #var_table in each iteration of the loop, that's why you get all the records times 4 (the count of records in #var_table).
However, you don't need a loop at all, and you should strive to avoid loops any time you are using SQL anyway, since SQL works best with a set based approach and not a procedural approach (For more information, read RBAR: ‘Row By Agonizing Row’ and What is RBAR? How can I avoid it?)
Instead of a loop, you can simply use the row_number() window function to get the n_progressive value:
insert into #Tmptable( n_progressive, name, id_numeric)
select row_number() over(order by name), name, id_numeric
from #var_table

Answer 2

You are not restricting the INSERT to read one row from your source table, you're copying the whole table multiple times. To directly fix what you are trying to do, you should do something like this...
while(#i<#c) begin
set #n_progressive = #n_progressive + 1
insert into
#Tmptable( n_progressive , name , id_numeric )
select
#n_progressive, name, id_numeric
from
#var_table
WHERE
id_number = #i -- Only one row
SET #i = #i + 1 -- Move to the next row
end
A better idea could be to use ROW_NUMBER(), avoiding the need for the loop and much of the other boiler plate code.
insert into
#Tmptable( n_progressive , name , id_numeric )
select
ROW_NUMBER() OVER (ORDER BY id_numeric),
name,
id_numeric
from
#var_table
A better idea still could be to use an identity column, and let the table do the number allocations.
create table
#tmp_table(
n_progressive int IDENTITY(1,1),
name char(10) ,
id_ numeric(11,0)
)
insert into #Tmptable(name , id_numeric )
select name, id_numeric
from MainTable
ORDER BY id_numeric

Answer 3

Does this do what you want?
with n as (
select 1 as n
union all
select n + 1
from n
where n < #n_limit
)
select n.n, name + cast(n.n as varchar(255)), n.n as numeric_id
from n
option (maxrecursion 0);