在字段名前加上 DISTINCT
SELECT department_id FROM employees;
这样操作有的部门编号就是重复的,只是看用到了那些,所以要去重
SELECT DISTINCT department_id FROM employees;
在字段名前加上 DISTINCT
SELECT department_id FROM employees;
这样操作有的部门编号就是重复的,只是看用到了那些,所以要去重
SELECT DISTINCT department_id FROM employees;