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leetcode/problem/combine-two-tables.html

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+<p>Table: <code>Person</code></p>
+
+<pre>
++-------------+---------+
+| 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.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Table: <code>Address</code></p>
+
+<pre>
++-------------+---------+
+| 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.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Write an SQL query to report the first name, last name, city, and state of each person in the <code>Person</code> table. If the address of a <code>personId</code> is not present in the <code>Address</code> table, report <code>null</code> instead.</p>
+
+<p>Return the result table in <strong>any order</strong>.</p>
+
+<p>The query result format is in the following example.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> 
+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 |
++-----------+----------+---------------+------------+
+<strong>Output:</strong> 
++-----------+----------+---------------+----------+
+| firstName | lastName | city          | state    |
++-----------+----------+---------------+----------+
+| Allen     | Wang     | Null          | Null     |
+| Bob       | Alice    | New York City | New York |
++-----------+----------+---------------+----------+
+<strong>Explanation:</strong> 
+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.
+</pre>