(STOREDPROC) Generated SELECT statement: looking for the right syntax to use near NULL

Question

I am using stored procedure in creating table adapter. This is my syntax:

DELIMITER $$

DROP PROCEDURE IF EXISTS `lcs_rdb`.`sp_EmployeeListReport`$$

CREATE DEFINER=`root`@`localhost` PROCEDURE `sp_EmployeeListReport`(in where_clause TEXT)
BEGIN
        SET @sql = CONCAT("SELECT        
                emp.employee_id, 
                group_concat(distinct `ext`.`extension_number` separator ',') AS extension_number,
                emp.employee_lastname, emp.employee_firstname, 
                dept.department_description, 
                divs.division_description, 
                grps.group_description, 
                st.site_name, emp.audit_date,
                group_concat(distinct `cst_ctr`.`cost_center_description` separator ',') AS cost_center_description
                FROM employees emp INNER JOIN
                 employee_extensions emp_ext ON emp_ext.employee_id = emp.employee_id INNER JOIN
                 extensions ext ON ext.extension_id = emp_ext.extension_id INNER JOIN
                 departments dept ON emp.department_id = dept.department_id INNER JOIN
                 divisions divs ON dept.division_id = divs.division_id INNER JOIN
                 groups grps ON divs.group_id = grps.group_id INNER JOIN
                 sites st ON emp.site_id = st.site_id LEFT OUTER JOIN
                 employee_cost_centers emp_cstctr ON emp.employee_id = emp_cstctr.employee_id LEFT OUTER JOIN
                 cost_centers cst_ctr ON emp_cstctr.cost_center_id = cst_ctr.cost_center_id
                where ", where_clause ,"");
 PREPARE stmt FROM @sql;
 EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
   END$$

DELIMITER ;

This is the error when I executed it:
"Generated SELECT statement. You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'NULL' at line 1"

I think, the problem is in the where clause. But I don't know how to fix it. Please help. Thanks.

Answer 1

CONCAT() returns NULL if any values are NULL. Perhaps you want something like:

CONCAT('select . . .',
       COALESCE(where_clause, '1 = 1'))