replace-employee-id-with-the-unique-identifier

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Database

Table: <code>Employees</code>

<pre>
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| name | varchar |
+---------------+---------+
id is the primary key (column with unique values) for this table.
Each row of this table contains the id and the name of an employee in a company.
</pre>

&nbsp;

Table: <code>EmployeeUNI</code>

<pre>
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| unique_id | int |
+---------------+---------+
(id, unique_id) is the primary key (combination of columns with unique values) for this table.
Each row of this table contains the id and the corresponding unique id of an employee in the company.
</pre>

&nbsp;

Write a solution to show the unique ID of each user, If a user does not have a unique ID replace just show <code>null</code>.

Return the result table in any order.

The result format is in the following example.

&nbsp;
Example 1:

<pre>
Input: 
Employees table:
+----+----------+
| id | name |
+----+----------+
| 1 | Alice |
| 7 | Bob |
| 11 | Meir |
| 90 | Winston |
| 3 | Jonathan |
+----+----------+
EmployeeUNI table:
+----+-----------+
| id | unique_id |
+----+-----------+
| 3 | 1 |
| 11 | 2 |
| 90 | 3 |
+----+-----------+
Output: 
+-----------+----------+
| unique_id | name |
+-----------+----------+
| null | Alice |
| null | Bob |
| 2 | Meir |
| 3 | Winston |
| 1 | Jonathan |
+-----------+----------+
Explanation: 
Alice and Bob do not have a unique ID, We will show null instead.
The unique ID of Meir is 2.
The unique ID of Winston is 3.
The unique ID of Jonathan is 1.
</pre>

replace_employee_id

Replace Employee ID With The Unique Identifier

<code>Employees</code> 表：

<pre>
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| name | varchar |
+---------------+---------+
在 SQL 中，id 是这张表的主键。
这张表的每一行分别代表了某公司其中一位员工的名字和 ID 。
</pre>

&nbsp;

<code>EmployeeUNI</code>&nbsp;表：

<pre>
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| unique_id | int |
+---------------+---------+
在 SQL 中，(id, unique_id) 是这张表的主键。
这张表的每一行包含了该公司某位员工的 ID 和他的唯一标识码（unique ID）。
</pre>

&nbsp;

展示每位用户的 唯一标识码（unique ID ）；如果某位员工没有唯一标识码，使用 null 填充即可。

你可以以 任意 顺序返回结果表。

返回结果的格式如下例所示。

&nbsp;

示例 1：

<pre>
<code>输入：
Employees</code> 表:
+----+----------+
| id | name |
+----+----------+
| 1 | Alice |
| 7 | Bob |
| 11 | Meir |
| 90 | Winston |
| 3 | Jonathan |
+----+----------+
<code>EmployeeUNI</code> 表:
+----+-----------+
| id | unique_id |
+----+-----------+
| 3 | 1 |
| 11 | 2 |
| 90 | 3 |
+----+-----------+
输出：
+-----------+----------+
| unique_id | name |
+-----------+----------+
| null | Alice |
| null | Bob |
| 2 | Meir |
| 3 | Winston |
| 1 | Jonathan |
+-----------+----------+
解释：
Alice and Bob 没有唯一标识码, 因此我们使用 null 替代。
Meir 的唯一标识码是 2 。
Winston 的唯一标识码是 3 。
Jonathan 唯一标识码是 1 。</pre>