Table: Project
\n+-------------+---------+\n| Column Name | Type |\n+-------------+---------+\n| project_id | int |\n| employee_id | int |\n+-------------+---------+\n(project_id, employee_id) is the primary key of this table.\nemployee_id is a foreign key to Employee table.\nEach row of this table indicates that the employee with employee_id is working on the project with project_id.\n\n\n\n\n
Table: Employee
\n+------------------+---------+\n| Column Name | Type |\n+------------------+---------+\n| employee_id | int |\n| name | varchar |\n| experience_years | int |\n+------------------+---------+\nemployee_id is the primary key of this table. It's guaranteed that experience_years is not NULL.\nEach row of this table contains information about one employee.\n\n\n
\n\n
Write an SQL query that reports the average experience years of all the employees for each project, rounded to 2 digits.
\n\nReturn the result table in any order.
\n\nThe query result format is in the following example.
\n\n\n
Example 1:
\n\n\nInput: \nProject table:\n+-------------+-------------+\n| project_id | employee_id |\n+-------------+-------------+\n| 1 | 1 |\n| 1 | 2 |\n| 1 | 3 |\n| 2 | 1 |\n| 2 | 4 |\n+-------------+-------------+\nEmployee table:\n+-------------+--------+------------------+\n| employee_id | name | experience_years |\n+-------------+--------+------------------+\n| 1 | Khaled | 3 |\n| 2 | Ali | 2 |\n| 3 | John | 1 |\n| 4 | Doe | 2 |\n+-------------+--------+------------------+\nOutput: \n+-------------+---------------+\n| project_id | average_years |\n+-------------+---------------+\n| 1 | 2.00 |\n| 2 | 2.50 |\n+-------------+---------------+\nExplanation: 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\n\n", "translatedTitle": "项目员工 I", "translatedContent": "
项目表 Project：
\n+-------------+---------+\n| Column Name | Type |\n+-------------+---------+\n| project_id | int |\n| employee_id | int |\n+-------------+---------+\n主键为 (project_id, employee_id)。\nemployee_id 是员工表 Employee 表的外键。\n\n\n员工表 Employee：
\n+------------------+---------+\n| Column Name | Type |\n+------------------+---------+\n| employee_id | int |\n| name | varchar |\n| experience_years | int |\n+------------------+---------+\n主键是 employee_id。\n\n\n
\n\n
请写一个 SQL 语句，查询每一个项目中员工的 平均 工作年限，精确到小数点后两位。
\n\n查询结果的格式如下：
\n\n\nProject 表：\n+-------------+-------------+\n| project_id | employee_id |\n+-------------+-------------+\n| 1 | 1 |\n| 1 | 2 |\n| 1 | 3 |\n| 2 | 1 |\n| 2 | 4 |\n+-------------+-------------+\n\nEmployee 表：\n+-------------+--------+------------------+\n| employee_id | name | experience_years |\n+-------------+--------+------------------+\n| 1 | Khaled | 3 |\n| 2 | Ali | 2 |\n| 3 | John | 1 |\n| 4 | Doe | 2 |\n+-------------+--------+------------------+\n\nResult 表：\n+-------------+---------------+\n| project_id | average_years |\n+-------------+---------------+\n| 1 | 2.00 |\n| 2 | 2.50 |\n+-------------+---------------+\n第一个项目中，员工的平均工作年限是 (3 + 2 + 1) / 3 = 2.00；第二个项目中，员工的平均工作年限是 (3 + 2) / 2 = 2.50\n\n", "isPaidOnly": false, "difficulty": "Easy", "likes": 53, "dislikes": 0, "isLiked": null, "similarQuestions": "[]", "contributors": [], "langToValidPlayground": "{\"cpp\": false, \"java\": false, \"python\": false, \"python3\": false, \"mysql\": false, \"mssql\": false, \"oraclesql\": 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