Can I use variable in condition statement as value with where condition that test that value - sql

Question

I have the following stored procedure:
ALTER proc [dbo].[insertperoll] #name nvarchar(50) , #snum int , #gnum int
as
DECLARE #value nvarchar(10)
SET #value = 's'+CONVERT(nvarchar(50),#snum)
DECLARE #sqlText nvarchar(1000);
DECLARE #sqlText2 nvarchar(1000);
DECLARE #sqlText3 nvarchar(1000);
declare #g nvarchar(50) = '''g1'''
SET #sqlText = N'SELECT ' + #value + N' FROM dbo.GrideBtable'
SET #sqlText2 = ' where Gnumber = '+#g --here is the problem it error invalid column name -- the #g is value from the table condition
set #sqlText3 = #sqlText+#sqlText2
Exec (#sqlText3) -- here how can i save the result of the exec into varibale
declare #sal nvarchar(50) = #sqlText3
insert employ (name,Snumber,Gnumber,Salary) values(#name,#snum,#gnum,#sal)
QUESTION: How to put in condition variable gets value from the table when i exec it it think that the #g is column but its not its a value from the table to test it so i display one value after the exec the other QUESTION is how to save the result from the exec in variable and then use that value
I'm using SQL Server 2008 (9.0 RTM)
This will be a stored procedure
Thanks in advance

Answer 1

Not sure why you would go through all the loops to insert into the table where you can have a simple insert query like ..
ALTER PROC dbo.[insertperoll] #name nvarchar(50) , #snum int , #gnum int
AS
insert employ (name, Snumber, Gnumber, Salary)
select #name
, #sum
, #gnum
, case when #snum = 1 then s1
when #snum = 2 then s2
when #snum = 3 then s3
when #snum = 4 then s4
end as Salary
from dbo.GrideBtable
where Gnumber = #gnum

Answer 2

If your intent is to have the proc retrieve a salary value from a column determined from the parameter snum and then make an insert into employ using the values passed as parameters and the salary retrieved I think you could refactor your procedure to this:
CREATE proc [dbo].[insertperoll] #name nvarchar(50) , #snum int , #gnum int AS
DECLARE #g NVARCHAR(50) = 'g1'
DECLARE #sql NVARCHAR(MAX);
SET #sql = N'INSERT employ (name,Snumber,Gnumber,Salary) '
SET #sql += N'SELECT ' + QUOTENAME(#name, '''')
SET #sql += N', ' + CAST(#snum AS NVARCHAR(50))
SET #sql += N', ' + CAST(#gnum AS NVARCHAR(50))
SET #sql += N', s' + CAST(#snum AS NVARCHAR(50))
SET #sql += N' FROM dbo.GrideBtable'
SET #sql += N' WHERE Gnumber = ' + QUOTENAME(#g, '''')
EXEC (#sql)
Of course you could add the #g variable to the procedure parameters instead of having it hard coded in the procedure and call it as:
EXEC insertperoll #name='john', #snum=10, #gnum=100, #g='g1'
Sample SQL Fiddle (with some assumptions made about table structure)

Answer 3

You could do this using sp_executesql instead of exec() since this will allow you to use parameters, you can use an output parameter to get the value from the query:
DECLARE #SQL NVARCHAR(MAX) = N'SELECT #val = ' + CONVERT(NVARCHAR(10),#snum) +
N' FROM dbo.GrideBtable WHERE Gnumber = #G1';
DECLARE #val INT; -- NOT SURE OF DATATYPE REQUIRED
EXECUTE sp_executesql #SQL, N'#G1 VARCHAR(20), #val INT OUT', 'G1', #val OUT;