SQL Server: I wonder what syntax error is near else - sql-server

Question

I'm tring to create a procedure. And when I set #age after setting #flag, something is wrong. But either I tried to delete set #age or set #flag it would work.
error:there is a syntax error near else
I wonder what caused this. Thanks for help.
select * from sc
if exists(select *
from sysobjects
where name='pro5' and type ='P')
drop procedure pro5
go
create procedure pro5 #stuNo char(10),#flag int output
as
declare #age int
begin
set #age=0
set #flag=1
if exists(select *
from sc
where sno=#stuNo)
set #flag=0
set #age=0
else
delete
from student
where sno=#stuNO
end
return #age
go
declare #flag int
exec pro5 '991102',#flag output
if #flag=1
print 'success'
else
print 'failure'

Answer 1

You need to define a begin and end around all lines in your if statement which by default only assumes a single line belongs to the "if" block:
if exists(select * from sc where sno=#stuNo)
begin
set #flag=0
set #age=0
end
else
delete
from student
where sno=#stuNO
However you could simplify a little since you don't need to also set age which is already 0. I'm assuming you actualy might need to set #age to 1 and this is a cut-down example of your code and you can amend as required:
create procedure pro5 #stuNo char(10), #flag int output
as
declare #age int = 0;
if exists(select * from sc where sno = #stuNo)
set #flag = 0
else
begin
delete from student where sno = #stuNO;
set #flag = 1;
end
return #age;

Answer 2

changed syntax a bit:
create procedure pro5 (
#stuNo char(10),
#flag int output
)
as
begin
declare #age int
set #age=0
set #flag=1
if exists(select *
from sc
where sno=#stuNo)
begin
set #flag=0
set #age=0
end
else
delete
from student
where sno=#stuNO
return #age
end
go
declare #flag int
exec pro5 '991102',#flag output
if #flag=1
print 'success'
else
print 'failure'