group_concat函数详解

来自:http://hchmsguo.iteye.com/blog/555543
MySQL中group_concat函数

完整的语法如下：

GROUP_CONCAT([DISTINCT] expr [,expr ...] [ORDER BY {unsigned_integer | col_name | expr} [ASC | DESC] [,col_name ...]] [SEPARATOR str_val])
即
group_concat([DISTINCT] 要连接的字段 [Order BY ASC/DESC 排序字段] [Separator '分隔符'])

基本查询

Sql代码  收藏代码
select * from aa; 

+------+------+
| id| name |
+------+------+
|1 | 10|
|1 | 20|
|1 | 20|
|2 | 20|
|3 | 200 |
|3 | 500 |
+------+------+
6 rows in set (0.00 sec)

以id分组，把name字段的值打印在一行，逗号分隔(默认)

Sql代码  收藏代码
select id,group_concat(name) from aa group by id; 

+------+--------------------+
| id| group_concat(name) |
+------+--------------------+
|1 | 10,20,20|
|2 | 20 |
|3 | 200,500|
+------+--------------------+
3 rows in set (0.00 sec)

以id分组，把name字段的值打印在一行，分号分隔

Java代码  收藏代码
select id,group_concat(name separator ';') from aa group by id; 

+------+----------------------------------+
| id| group_concat(name separator ';') |
+------+----------------------------------+
|1 | 10;20;20 |
|2 | 20|
|3 | 200;500 |
+------+----------------------------------+
3 rows in set (0.00 sec)

以id分组，把去冗余的name字段的值打印在一行，

逗号分隔

Sql代码  收藏代码
select id,group_concat(distinct name) from aa group by id; 

+------+-----------------------------+
| id| group_concat(distinct name) |
+------+-----------------------------+
|1 | 10,20|
|2 | 20 |
|3 | 200,500 |
+------+-----------------------------+
3 rows in set (0.00 sec)

以id分组，把name字段的值打印在一行，逗号分隔，以name排倒序

Sql代码  收藏代码
select id,group_concat(name order by name desc) from aa group by id; 

+------+---------------------------------------+
| id| group_concat(name order by name desc) |
+------+---------------------------------------+
|1 | 20,20,10 |
|2 | 20|
|3 | 500,200|
+------+---------------------------------------+
3 rows in set (0.00 sec)

测试sql，项目中用到的。
Sql代码  收藏代码
SELECT 
        EMPLOYEES.EMPID 
        ,EMPLOYEES.EMPNAME 
        ,DEPARTMENTS.DEPARTMENTNAME 
        ,EMPLOYEES.DEPTID 
        ,EMPLOYEES.EMPPWD 
        ,EMPLOYEES.INSIDEEMAIL 
        ,EMPLOYEES.OUTSIDEEMAIL 
        ,EMPLOYEES.DELEFLAG 
        ,EMPLOYEES.EMPCLASS 
        ,(CONCAT('[', <span style="color: #ff0000;">GROUP_CONCAT</span> 
(ROLE.Role_Name SEPARATOR '],['), ']')) AS ROLENAME 
        ,(concat( '[', ( 
            SELECT 
                    <span style="color: #ff0000;">GROUP_CONCAT</span> 
(DEPARTMENTS.DEPARTMENTNAME separator '],[') 
                FROM 
                    EMP_ROLE_DEPT 
                        LEFT JOIN DEPARTMENTS 
                            ON ( 
                                DEPARTMENTS.DEPARTMENTID = EMP_ROLE_DEPT.DEPTID 
                                AND DEPARTMENTS.DELEFLAG = 0 
                            ) 
                GROUP BY 
                    EMP_ROLE_DEPT.EMPID 
                HAVING 
                    EMP_ROLE_DEPT.EMPID = EMPLOYEES.EMPID 
        ),']')) AS DEPARTMENTRIGHT 
    FROM 
        EMPLOYEES 
            LEFT JOIN DEPARTMENTS 
                ON ( 
                    DEPARTMENTS.DEPARTMENTID = EMPLOYEES.DEPTID 
                    AND DEPARTMENTS.DELEFLAG = 0 
                ) 
            LEFT JOIN ROLE_EMP 
                ON (ROLE_EMP.EMP_ID = EMPLOYEES.EMPID) 
            LEFT JOIN ROLE 
                ON (ROLE_EMP.ROLE_ID = ROLE.ROLE_ID) 
<span style="color: #ff0000;">    GROUP BY 
        EMPLOYEES.EMPID</span> 
 
    HAVING 
        EMPLOYEES.EMPID LIKE '%%' 
        AND EMPLOYEES.EMPNAME LIKE '%%' 
        AND EMPLOYEES.DELEFLAG = 0 
        AND ( 
            EMPLOYEES.EMPCLASS = '1' 
            OR EMPLOYEES.EMPCLASS = '2' 
        ) 
        AND EMPLOYEES.DEPTID = '001' LIMIT 0 
        ,16