这是一个有效的 SQL 声明吗？

Question

问题：哪支球队拥有最年轻的运动员，那名运动员叫什么名字？

SELECT athleteFirstName, athleteLastName, teamName
FROM team t JOIN athlete a ON t.teamId = a.teamId
WHERE athleteDateOfBirth = (SELECT MAX(athleteDateOfBirth)
                            FROM team JOIN athlete ON team.teamId = athlete.teamId)
GROUP BY teamName, athleteFirstName, athleteLastName;

所以我连接了两个表并试图解决这个问题。我已经尝试过 DATEDIFF，但我得到的只是错误。许多不同的错误。

那个子查询行得通吗？

比如，它是否有意义，或者因为我没有使用过 DATEDIFF，我的老师会把它标记为不正确吗？如果我需要在子查询中添加 GROUP BY 语句，我也有点困惑。

Answer 1

试试这个找到最小的：

在 sql 服务器中：

SELECT athleteFirstName, athleteLastName, teamName 
FROM team t JOIN athlete a ON t.teamId = a.teamId
where athleteDateOfBirth= (select top 1 athleteDateOfBirth from athlete 
order by athleteDateOfBirth desc )

在mysql中：

SELECT athleteFirstName, athleteLastName, teamName 
FROM team t JOIN athlete a ON t.teamId = a.teamId
where athleteDateOfBirth= (select athleteDateOfBirth from athlete 
order by athleteDateOfBirth desc limit 1)

Answer 2

试一试

SELECT athleteFirstName,
       athleteLastName,
       teamName
FROM team t
JOIN athlete a ON t.teamId = a.teamId
WHERE athleteDateOfBirth =
    (SELECT TOP(1) athlete.athleteDateOfBirth
     FROM athlete
     ORDER BY athlete.athleteDateOfBirth ASC)
GROUP BY teamName,
         athleteFirstName,
         athleteLastName;

Answer 3

正在将子查询中的 table 更改为 athlete。

SELECT athleteFirstName, athleteLastName, teamName
FROM team t JOIN athlete a ON t.teamId = a.teamId
WHERE athleteDateOfBirth = (SELECT MAX(athleteDateOfBirth) FROM athlete)

Answer 4

我认为您可以使用 Limit 或 TOP 关键字来实现它。对于 SQL 服务器使用 top，对于 MYSql/PostgreSQL 使用 Limit。
SQL 服务器：

Select top 1 t.TName AS TeamName,a.AName AthleteName,a.athleteDateOfBirth from teamT as t
INNER JOIN athleteT AS a ON t.TeamID=a.TeamID
ORDER BY athleteDateOfBirth DESC;

Link: Demo Link。

MySQL / PostgreSQL:

Select t.TName AS TeamName,a.AName AthleteName,a.athleteDateOfBirth from teamT as t
INNER JOIN athleteT AS a ON t.TeamID=a.TeamID
ORDER BY athleteDateOfBirth DESC
LIMIT 1;

LINK: Demo Code.

这是一个有效的 SQL 声明吗？

Is this a valid SQL statement?

sql

sql-server

subquery