存量题库数据更新

leetcode/problem/project-employees-i.html

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+<p>Table: <code>Project</code></p>
+
+<pre>
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| project_id  | int     |
+| employee_id | int     |
++-------------+---------+
+(project_id, employee_id) is the primary key of this table.
+employee_id is a foreign key to <code>Employee</code> table.
+Each row of this table indicates that the employee with employee_id is working on the project with project_id.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Table: <code>Employee</code></p>
+
+<pre>
++------------------+---------+
+| Column Name      | Type    |
++------------------+---------+
+| employee_id      | int     |
+| name             | varchar |
+| experience_years | int     |
++------------------+---------+
+employee_id is the primary key of this table. It&#39;s guaranteed that experience_years is not NULL.
+Each row of this table contains information about one employee.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Write an SQL query that reports the <strong>average</strong> experience years of all the employees for each project, <strong>rounded to 2 digits</strong>.</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 class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> 
+Project table:
++-------------+-------------+
+| project_id  | employee_id |
++-------------+-------------+
+| 1           | 1           |
+| 1           | 2           |
+| 1           | 3           |
+| 2           | 1           |
+| 2           | 4           |
++-------------+-------------+
+Employee table:
++-------------+--------+------------------+
+| employee_id | name   | experience_years |
++-------------+--------+------------------+
+| 1           | Khaled | 3                |
+| 2           | Ali    | 2                |
+| 3           | John   | 1                |
+| 4           | Doe    | 2                |
++-------------+--------+------------------+
+<strong>Output:</strong> 
++-------------+---------------+
+| project_id  | average_years |
++-------------+---------------+
+| 1           | 2.00          |
+| 2           | 2.50          |
++-------------+---------------+
+<strong>Explanation:</strong> The average experience years for the first project is (3 + 2 + 1) / 3 = 2.00 and for the second project is (3 + 2) / 2 = 2.50
+</pre>