单行子查询
#单行子查询:
#操作符:= != > >= < <=
#题目:查询工资大于149号员工工资的员工信息
SELECT salary
FROM employees
WHERE salary>(
SELECT salary
FROM employees
WHERE employee_id='149'
);
#返回job_id与141号员工相同,salary比143号员工多的员工姓名,job_id和工资
SELECT last_name,job_id,salary
FROM employees
WHERE job_id=(
SELECT job_id
FROM employees
WHERE employee_id=141
)
AND salary>(
SELECT salary
FROM employees
WHERE employee_id=143
);
#返回公司工资最少的员工的last_name,job_id和salary
SELECT last_name,job_id,salary
FROM employees
WHERE salary=(
SELECT MIN(salary)
FROM employees
);
#查询与141号员工的manager_id和department_id相同的其他员工的employee_id, manager_id,department_id
SELECT employee_id,manager_id,department_id
FROM employees
WHERE manager_id=(
SELECT manager_id
FROM employees
WHERE employee_id =141
)
AND department_id=(
SELECT department_id
FROM employees
WHERE employee_id =141
)
AND employee_id != 141;
#查询最低工资大于50号部门最低工资的部门id和其最低工资
SELECT department_id,MIN(salary)
FROM employees
GROUP BY department_id
HAVING MIN(salary)>(
SELECT MIN(salary)
FROM employees
WHERE department_id=50
);
#显式员工的employee_id,last_name和location。
其中,若员工department_id与location_id为1800 的department_id相同,
则location为’Canada’,其余则为’USA’。
SELECT employee_id,last_name,
CASE department_id WHEN(SELECT department_id FROM departments WHERE location_id=1800) THEN 'Canada'
ELSE 'USA' END "location"
FROM employees;