【SQL数据库】union 联集

接上一篇

1 员工名字union 客户名字

SELECT `name` 
FROM `employee`
UNION
SELECT `client_name` 
FROM `client`
UNION
SELECT `branch_name`
FROM `branch`;

如果想要branch_name，可以再加一个union

注意合并的时候，合并的数据类型要相同

每个表格取的资料属性数量要相同 

2 员工id+员工名字 union 客户id + 客户名字

SELECT `emp_id` AS `total_id`, `name` AS `total_name`
FROM `employee`
UNION
SELECT `client_id`, `client_name`
FROM `client`;

默认返回第一个的属性名

要改变属性名，加as

3 员工薪水 union 销售金额

SELECT `salary` AS `total_money` FROM `employee`
UNION
SELECT `total_sales` FROM `work_with`;