175 |
Combine Two Tables |
Table: Person
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| PersonId | int |
| FirstName | varchar |
| LastName | varchar |
+-------------+---------+
PersonId is the primary key column for this table.
Table: Address
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| AddressId | int |
| PersonId | int |
| City | varchar |
| State | varchar |
+-------------+---------+
AddressId is the primary key column for this table.
Write a SQL query for a report that provides the following information for each person in the Person table, regardless if there is an address for each of those people:
FirstName, LastName, City, State
开始直接用了where WA了 看了一下要输出null的情况 也就是address表可能对应不上person表 所以用左连接来做
# Write your MySQL query statement below
select firstname,lastname,city,state
from person left join
address on person.personid=address.personid
176 |
Second Highest Salary |
Write a SQL query to get the second highest salary from the Employee
table.
+----+--------+
| Id | Salary |
+----+--------+
| 1 | 100 |
| 2 | 200 |
| 3 | 300 |
+----+--------+
For example, given the above Employee table, the query should return 200
as the second highest salary. If there is no second highest salary, then the query should return null
.
+---------------------+
| SecondHighestSalary |
+---------------------+
| 200 |
+---------------------+
有点坑 又是null的条件 这是题解 IFNULL语句进行判断
SELECT IFNULL(
(SELECT DISTINCT Salary
FROM Employee
ORDER BY Salary DESC
LIMIT 1 OFFSET 1),
NULL) AS SecondHighestSalary
181 |
Employees Earning More Than Their Managers |
The Employee
table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id.
+----+-------+--------+-----------+ | Id | Name | Salary | ManagerId | +----+-------+--------+-----------+ | 1 | Joe | 70000 | 3 | | 2 | Henry | 80000 | 4 | | 3 | Sam | 60000 | NULL | | 4 | Max | 90000 | NULL | +----+-------+--------+-----------+
Given the Employee
table, write a SQL query that finds out employees who earn more than their managers. For the above table, Joe is the only employee who earns more than his manager.
+----------+ | Employee | +----------+ | Joe | +----------+
# Write your MySQL query statement below
select X.Name as 'Employee'
from Employee X,Employee Y
where X.salary>Y.salary and X.ManagerID=y.id
177 |
Nth Highest Salary |
Write a SQL query to get the nth highest salary from the Employee
table.
+----+--------+ | Id | Salary | +----+--------+ | 1 | 100 | | 2 | 200 | | 3 | 300 | +----+--------+
For example, given the above Employee table, the nth highest salary where n = 2 is 200
. If there is no nth highest salary, then the query should return null
.
+------------------------+ | getNthHighestSalary(2) | +------------------------+ | 200 | +------------------------+
Seen this question in a real interview before?
CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
DECLARE M INT;
SET M=N-1;
RETURN (
# Write your MySQL query statement below.
select ifnull((
select distinct salary
from employee
order by salary desc
limit m,1),null)
);
END