mysql - 使用存储过程计算团队中的人数

Question

我想创建一个存储过程，它接受球队名称和年份，并返回该特定球队在该特定年份的球员人数。我正在使用 MYSQL，下面列出了我正在使用的表:

Person     (personID, name, phone, email, year)
Player     (personID, dateOfBirth, school)
playerTeam (personID, teamID)
Team       (teamID, teamName, ageGroup)

到目前为止，我已经尝试加入表并仅在 teamName 和 Person.year = 输入参数的情况下计算 personID 但无济于事。有什么想法吗？

提交这个问题后，通过反复试验，我能够使用以下语句让它工作:

DELIMITER //

CREATE PROCEDURE teamSize (IN team VARCHAR (30), IN YEAR INT) 
BEGIN
          SELECT 
                    COUNT(Person.personID) NumOfPlayers 
          FROM
                    Person AS p,
                    Player,
                    playerTeam,
                    Team 
          WHERE Person.personID = Player.personID 
                    AND Player.personID = playerTeam.personID 
                    AND Team.teamID = playerTeam.teamID 
                    AND Team.teamName = team 
                    AND Person.year = YEAR ;
END //

DELIMITER ;

CALL teamSize('Pirates', 1991);

有没有办法使用连接等来简化这个，因为目前它有点困惑。

Answer 1

我不确定你是否想要这样:

DELIMITER //

CREATE PROCEDURE GetPlayerCount (
          IN oTeamName VARCHAR (50),
          IN oYear INT
) AS 
BEGIN
          SELECT 
                    COUNT(a.PersonID) NoOfPlayers 
          FROM
                    Person a 
                    INNER JOIN PlayerTeam b 
                              ON a.PersonID = b.PersonID 
                    INNER JOIN Team c 
                              ON b.TeamID = c.TeamID 
          WHERE b.TeamName = oTeamName 
                    AND a.Year = oYear ;
END //

DELIMITER ;

但我认为这是你想要的。

用法:

CALL GetPlayerCount('TeamDog', 2012);