mysql - (STOREDPROC) 生成的 SELECT 语句 : looking for the right syntax to use near NULL

Question

我在创建表适配器时使用存储过程。这是我的语法:

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 ;

这是我执行时的错误:
“生成的 SELECT 语句。 您的 SQL 语法有误；检查与您的 MySQL 服务器版本对应的手册，了解在第 1 行的“NULL”附近使用的正确语法”

我认为，问题出在 where 子句中。但我不知道如何解决它。请帮忙。谢谢。

Answer 1

如果任何值为 NULL，

CONCAT() 返回 NULL。也许你想要这样的东西:

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