sybase - simple concatenation

Question

I am trying to create a utility stored proc, that can take a parameter and query a handy table for retrieving some quick info. For this I need to add '%' character before and after the param passed so as to use it in the query with like, as shown below.

Working code - if hardcoded

select some_field from TABLE where nm_field like ('%'+'abc'+'%')

But when I try to use the same with a variable, I get lesser results as compared to above query

declare @nm char(100)
select @nm = 'abc'
select some_field from TABLE where nm_field like ('%'+@abc+'%')

On some investigation, trial and error, the following select shows that '%' is added only before the param, and not at both sides.

declare @name char(20), @other char(20)
select @name = 'abc'
select @other = ('%' + @name + '%')
select @other

Expected Output

%abc%

But actual output

%abc

I am using Sybase ASE-12.5.4

Can you please help me out with what is going wrong here?

Answer 1

Try to change @nm type to varchar as below

declare @nm varchar(100) 
select @nm = 'abc'
select some_field from TABLE where nm_field like ('%'+@abc+'%')

Char type has constant size and db fill a gap using spaces

declare @nm char(100) 
select @nm = 'abc' 

below select

select @nm

will return abc and 97 spaces.

Answer 2

It seems, I have found the correct answer. It's the usage of char that is leading to this behaviour, since it is of fixed size. varchar isn't such and hence the concatenation works as expected.

With char, we need to add trim so that concatenation happens as expected

declare @str char(100)
select @str ='abc'
select ('%'+ltrim(rtrim(@str))+'%')

Output

%abc%