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Updated readmes.
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‎src/main/kotlin/g0101_0200/s0175_combine_two_tables/readme.md‎

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Table: `Person`
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+-------------+---------+ | Column Name | Type | +-------------+---------+ | personId | int | | lastName | varchar | | firstName | varchar | +-------------+---------+ personId is the primary key column for this table. This table contains information about the ID of some persons and their first and last names.
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+-------------+---------+
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| Column Name | Type |
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+-------------+---------+
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| personId | int |
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| lastName | varchar |
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| firstName | varchar |
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+-------------+---------+
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personId is the primary key column for this table.
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This table contains information about the ID of some persons and their first and last names.
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Table: `Address`
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+-------------+---------+ | Column Name | Type | +-------------+---------+ | addressId | int | | personId | int | | city | varchar | | state | varchar | +-------------+---------+ addressId is the primary key column for this table. Each row of this table contains information about the city and state of one person with ID = PersonId.
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+-------------+---------+
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| Column Name | Type |
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+-------------+---------+
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| addressId | int |
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| personId | int |
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| city | varchar |
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| state | varchar |
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+-------------+---------+
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addressId is the primary key column for this table.
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Each row of this table contains information about the city and state of one person with ID = PersonId.
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Write an SQL query to report the first name, last name, city, and state of each person in the `Person` table. If the address of a `personId` is not present in the `Address` table, report `null` instead.
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@@ -20,8 +39,33 @@ The query result format is in the following example.
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**Example 1:**
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**Input:** Person table: +----------+----------+-----------+ | personId | lastName | firstName | +----------+----------+-----------+ | 1 | Wang | Allen | | 2 | Alice | Bob | +----------+----------+-----------+ Address table: +-----------+----------+---------------+------------+ | addressId | personId | city | state | +-----------+----------+---------------+------------+ | 1 | 2 | New York City | New York | | 2 | 3 | Leetcode | California | +-----------+----------+---------------+------------+
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**Input:**
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**Output:** +-----------+----------+---------------+----------+ | firstName | lastName | city | state | +-----------+----------+---------------+----------+ | Allen | Wang | Null | Null | | Bob | Alice | New York City | New York | +-----------+----------+---------------+----------+
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Person table:
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+----------+----------+-----------+
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| personId | lastName | firstName |
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+----------+----------+-----------+
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| 1 | Wang | Allen |
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| 2 | Alice | Bob |
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+----------+----------+-----------+
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Address table:
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+-----------+----------+---------------+------------+
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| addressId | personId | city | state |
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+-----------+----------+---------------+------------+
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| 1 | 2 | New York City | New York |
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| 2 | 3 | Leetcode | California |
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+-----------+----------+---------------+------------+
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**Explanation:** There is no address in the address table for the personId = 1 so we return null in their city and state. addressId = 1 contains information about the address of personId = 2.
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**Output:**
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+-----------+----------+---------------+----------+
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| firstName | lastName | city | state |
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+-----------+----------+---------------+----------+
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| Allen | Wang | Null | Null |
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| Bob | Alice | New York City | New York |
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+-----------+----------+---------------+----------+
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**Explanation:**
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There is no address in the address table for the personId = 1 so we return null in their city and state. addressId = 1 contains information about the address of personId = 2.

‎src/main/kotlin/g0101_0200/s0176_second_highest_salary/readme.md‎

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Table: `Employee`
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+-------------+------+ | Column Name | Type | +-------------+------+ | id | int | | salary | int | +-------------+------+ id is the primary key column for this table. Each row of this table contains information about the salary of an employee.
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+-------------+------+
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| Column Name | Type |
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+-------------+------+
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| id | int |
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| salary | int |
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+-------------+------+
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id is the primary key column for this table.
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Each row of this table contains information about the salary of an employee.
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Write an SQL query to report the second highest salary from the `Employee` table. If there is no second highest salary, the query should report `null`.
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The query result format is in the following example.
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**Example 1:**
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**Input:** Employee table: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | | 2 | 200 | | 3 | 300 | +----+--------+
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**Input:**
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**Output:** +---------------------+ | SecondHighestSalary | +---------------------+ | 200 | +---------------------+
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Employee table:
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+----+--------+
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| id | salary |
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+----+--------+
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| 1 | 100 |
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| 2 | 200 |
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| 3 | 300 |
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+----+--------+
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**Output:**
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+---------------------+
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| SecondHighestSalary |
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+---------------------+
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| 200 |
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+---------------------+
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**Example 2:**
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**Input:** Employee table: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | +----+--------+
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**Input:**
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Employee table:
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+----+--------+
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| id | salary |
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+----+--------+
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| 1 | 100 |
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+----+--------+
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**Output:**
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**Output:** +---------------------+ | SecondHighestSalary | +---------------------+ | null | +---------------------+
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+---------------------+
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| SecondHighestSalary |
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+---------------------+
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| null |
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+---------------------+

‎src/main/kotlin/g0101_0200/s0177_nth_highest_salary/readme.md‎

Lines changed: 42 additions & 6 deletions
Original file line numberDiff line numberDiff line change
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Table: `Employee`
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+-------------+------+ | Column Name | Type | +-------------+------+ | id | int | | salary | int | +-------------+------+ id is the primary key column for this table. Each row of this table contains information about the salary of an employee.
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+-------------+------+
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| Column Name | Type |
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+-------------+------+
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| id | int |
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| salary | int |
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+-------------+------+
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id is the primary key column for this table. Each row of this table contains information about the salary of an employee.
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Write an SQL query to report the <code>n<sup>th</sup></code> highest salary from the `Employee` table. If there is no <code>n<sup>th</sup></code> highest salary, the query should report `null`.
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Write an SQL query to report the `nth` highest salary from the `Employee` table. If there is no `nth` highest salary, the query should report `null`.
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The query result format is in the following example.
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**Example 1:**
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**Input:** Employee table: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | | 2 | 200 | | 3 | 300 | +----+--------+ n = 2
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**Input:**
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**Output:** +------------------------+ | getNthHighestSalary(2) | +------------------------+ | 200 | +------------------------+
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Employee table:
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+----+--------+
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| id | salary |
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+----+--------+
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| 1 | 100 |
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| 2 | 200 |
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| 3 | 300 |
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+----+--------+
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n = 2
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**Output:**
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+------------------------+
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| getNthHighestSalary(2) |
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+------------------------+
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| 200 |
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+------------------------+
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**Example 2:**
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**Input:** Employee table: +----+--------+ | id | salary | +----+--------+ | 1 | 100 | +----+--------+ n = 2
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**Input:**
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Employee table:
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+----+--------+
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| id | salary |
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+----+--------+
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| 1 | 100 |
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+----+--------+
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n = 2
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**Output:**
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**Output:** +------------------------+ | getNthHighestSalary(2) | +------------------------+ | null | +------------------------+
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+------------------------+
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| getNthHighestSalary(2) |
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+------------------------+
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| null |
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+------------------------+

‎src/main/kotlin/g0101_0200/s0178_rank_scores/readme.md‎

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Table: `Scores`
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+-------------+---------+ | Column Name | Type | +-------------+---------+ | id | int | | score | decimal | +-------------+---------+ id is the primary key for this table. Each row of this table contains the score of a game. Score is a floating point value with two decimal places.
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+-------------+---------+
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| Column Name | Type |
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+-------------+---------+
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| id | int |
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| score | decimal |
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+-------------+---------+
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id is the primary key for this table.
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Each row of this table contains the score of a game. Score is a floating point value with two decimal places.
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Write an SQL query to rank the scores. The ranking should be calculated according to the following rules:
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**Example 1:**
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**Input:** Scores table: +----+-------+ | id | score | +----+-------+ | 1 | 3.50 | | 2 | 3.65 | | 3 | 4.00 | | 4 | 3.85 | | 5 | 4.00 | | 6 | 3.65 | +----+-------+
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**Output:** +-------+------+ | score | rank | +-------+------+ | 4.00 | 1 | | 4.00 | 1 | | 3.85 | 2 | | 3.65 | 3 | | 3.65 | 3 | | 3.50 | 4 | +-------+------+
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**Input:**
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Scores table:
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+----+-------+
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| id | score |
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+----+-------+
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| 1 | 3.50 |
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| 2 | 3.65 |
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| 3 | 4.00 |
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| 4 | 3.85 |
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| 5 | 4.00 |
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| 6 | 3.65 |
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+----+-------+
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**Output:**
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+-------+------+
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| score | rank |
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+-------+------+
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| 4.00 | 1 |
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| 4.00 | 1 |
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| 3.85 | 2 |
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| 3.65 | 3 |
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| 3.65 | 3 |
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| 3.50 | 4 |
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+-------+------+

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