MySQL数据库的函数的使用：使用字符串拼接函数实现MySQL查询结果的拼接

GROUP_CONCAT(字段)

GROUP_CONCAT(字段 separator "分隔符")

GROUP_CONCAT(DISTINCT 字段 ORDER BY 字段 SEPARATOR "分隔符")

SELECT 
    employeeNumber,
    firstName,
    lastName,
    GROUP_CONCAT(DISTINCT customername ORDER BY customerName)
FROM
    employees
INNER JOIN customers ON customers.salesRepEmployeeNumber = employeeNumber
GROUP BY employeeNumber
ORDER BY firstName,lastname

CONCAT_WS("分隔符",str1,str2,...)

SELECT 
	CONCAT_WS(';',o.user_code,o.user_name) 
FROM sys_user o 
WHERE id = 5201314

CONCAT(str1,str2...)

SELECT 
	CONCAT(o.user_code,o.user_name) 
FROM sys_user o 
WHERE id = 5201314