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count 作用：计算指定字段在查询结果中出现sele的个数 SELECT COUNT(employee_id),COUNT(salary) FROM employees; salary是2000还是...0269 -
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1显示所有员工的姓名，部门号和部门名称 SELECT last_name,e.department_id,department_name from employees e LEFT JOIN dep...0247
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SELECT last_name,e.department_id, department_name FROM employees e LEFT OUTER JOIN departments d ON ...0349
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练习SELECT e.last_name,d.department_id,d.department_name FROM employees e,departments d WHERE e.depart...0254
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select 122106; Mysql 不支持full outer join 做满外查询 select employee_id,department_name from employees e fu...0287
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select employee_id,department_name from employees e right join departments d on e.department_id d.d...0287
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SELECT employee_id,department_name from employees e left join departments d on e.department_id d.de...0264
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