To concatenate a string uses sql concat function.
Syntax
expression + expression
expression += expression
CONCAT ( expression,expression )
Examples
SELECT 'abc'+'123';
SELECT CONCAT('abc','123');
SELECT ID, NAME + ' - ' + JOB FROM EMPLOYEES;
DECLARE @var_string varchar(100);
SET @var_string = 'String A.';
SET @var_string += ' String B.';
PRINT @var_string;