Question

我有两个表，一个：

INSERT INTO `fictional_companies` (`ID`, `name`)
VALUES
    (8209948, 'Moulon Rouge LTD'),
    (11399177, 'Burgers Burgers Burgers LTD');

和两个：

INSERT INTO `processed` (`ID`)
VALUES
    ('8209948');

我想从fictional_companies表中返回结果，但前提是processed表中不存在结果。

在示例情况下，将是结果：

(11399177, 'Burgers Burgers Burgers LTD')

Answer 1

LEFT JOIN基于与右侧表上的IS NULL检查的适当关系，将获得与右侧表不匹配的那些行

SELECT fc.*
FROM fictional_companies AS fc
LEFT JOIN processed AS p ON p.ID = fc.ID
WHERE p.ID IS NULL

使用Correlated Subqueries with Not Exists

可能是另一种方法

SELECT fc.*
FROM fictional_companies AS fc
WHERE NOT EXISTS (SELECT 1 FROM processed AS p 
                  WHERE p.ID = fc.ID)

Answer 2

使用左连接并检查右表中的空值仅在其中选择那些值

Attendance::where('attendance_date' , Carbon::now()->format('Y-m-d'))
        ->where('user_id', $this->id)
        ->where('scan_in_location', request()->scan_in_location)
        ->whereNotNull('scan_in_time')
        ->whereBetween('created_at' , [Carbon::now()->subMinutes(5), Carbon::now()])
        ->exists();

Answer 3

使用NOT IN：

SELECT * FROM `fictional_companies` WHERE `ID` NOT IN (SELECT `ID` FROM `processed`)

我相信代码很容易理解。

从一个表中返回的值不存在于另一个表中

3 个答案: