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leetcode-problemset/leetcode/problem/combine-two-tables.html

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2022-03-27 18:35:17 +08:00
<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>