leetcode

Description Table: Student +---------------------+---------+ | Column Name | Type | +---------------------+---------+ | student_id | int | | student_name | varchar | +---------------------+---------+ student_id is the primary key for this table. student_name is the name of the student. Table: Exam +---------------+---------+ | Column Name | Type | +---------------+---------+ | exam_id | int | | student_id | int | | score | int | +---------------+---------+ (exam_id, student_id) is the primary key for this table....

Description Table: UserActivity +---------------+---------+ | Column Name | Type | +---------------+---------+ | username | varchar | | activity | varchar | | startDate | Date | | endDate | Date | +---------------+---------+ There is no primary key for this table. It may contain duplicates. This table contains information about the activity performed by each user in a period of time. A person with username performed an activity from startDate to endDate....

Description Table: Visits +---------------+---------+ | Column Name | Type | +---------------+---------+ | user_id | int | | visit_date | date | +---------------+---------+ (user_id, visit_date) is the primary key for this table. Each row of this table indicates that user_id has visited the bank in visit_date. Table: Transactions +------------------+---------+ | Column Name | Type | +------------------+---------+ | user_id | int | | transaction_date | date | | amount | int | +------------------+---------+ There is no primary key for this table, it may contain duplicates....

題目 Table: Failed +--------------+---------+ | Column Name | Type | +--------------+---------+ | fail_date | date | +--------------+---------+ fail_date is the primary key for this table. This table contains the days of failed tasks. Table: Succeeded +--------------+---------+ | Column Name | Type | +--------------+---------+ | success_date | date | +--------------+---------+ success_date is the primary key for this table. This table contains the days of succeeded tasks. A system is running...

題目 Table: Employee +--------------+---------+ | Column Name | Type | +--------------+---------+ | id | int | | name | varchar | | salary | int | | departmentId | int | +--------------+---------+ id is the primary key column for this table. departmentId is a foreign key of the ID from the Department table. Each row of this table indicates the ID, name, and salary of an employee. It also...

題目 Table: Trips +-------------+----------+ | Column Name | Type | +-------------+----------+ | id | int | | client_id | int | | driver_id | int | | city_id | int | | status | enum | | request_at | date | +-------------+----------+ id is the primary key for this table. The table holds all taxi trips. Each trip has a unique id, while client_id and driver_id are foreign keys...

題目 Table: Employee +--------------+---------+ | Column Name | Type | +--------------+---------+ | id | int | | company | varchar | | salary | int | +--------------+---------+ id is the primary key column for this table. Each row of this table indicates the company and the salary of one employee. Write an SQL query to find the rows that contain the median salary of each company. While calculating the...

題目 Table: Numbers +-------------+------+ | Column Name | Type | +-------------+------+ | num | int | | frequency | int | +-------------+------+ num is the primary key for this table. Each row of this table shows the frequency of a number in the database. The median is the value separating the higher half from the lower half of a data sample. Write an SQL query to report the median...

題目 Table: Employee +-------------+------+ | Column Name | Type | +-------------+------+ | id | int | | month | int | | salary | int | +-------------+------+ (id, month) is the primary key for this table. Each row in the table indicates the salary of an employee in one month during the year 2020. Write an SQL query to calculate the cumulative salary summary for every employee in a...

題目 Table: Stadium +---------------+---------+ | Column Name | Type | +---------------+---------+ | id | int | | visit_date | date | | people | int | +---------------+---------+ visit_date is the primary key for this table. Each row of this table contains the visit date and visit id to the stadium with the number of people during the visit. No two rows will have the same visit_date, and as the...