Question

Customers            Holidays

id | name            customer_id | start  | end
---+------           ------------+--------+------
 1 | Peter           1           |   5    | 10
 2 | Simon           1           |  15    | 20
 3 | Mary            2           |   5    | 20

什么是有效的SQL查询，在特定日期为所有客户提供没有假期？ E.g。日期= 12

彼得
玛丽

这是否可以通过简单的SQL连接进行管理，还是需要使用子查询？

Answer 1

首先创建一个查找与您想要的相反的查询：在该特定日期有假期的客户：

SELECT DISTINCT name
FROM Customers
JOIN Holidays
ON id = customer_id
WHERE start <= 12 AND end >= 12

结果：

Simon

然后将此结果连接回customer表并选择连接失败的结果：

SELECT name
FROM Customers
LEFT JOIN (
    SELECT DISTINCT id
    FROM Customers
    JOIN Holidays
    ON id = customer_id
    WHERE start <= 12 AND end >= 12
) AS T1
ON Customers.id = T1.id
WHERE T1.id IS NULL

结果：

Peter
Mary

请注意，JOIN不是此处的唯一选择。您还可以使用NOT EXISTS，NOT IN或EXCEPT。由于您没有指定哪个数据库，我选择了JOIN，因为它是一种可移植且有效的方法，可以在所有主要关系数据库中执行此操作。

我使用的测试数据（取自问题）：

CREATE TABLE Holidays (customer_id INT NOT NULL, start INT NOT NULL, end INT NOT NULL);
INSERT INTO Holidays (customer_id, start, end) VALUES
(1, 5, 10),
(1, 15, 20),
(2, 5, 20);

CREATE TABLE Customers (id INT NOT NULL, name NVARCHAR(100) NOT NULL);
INSERT INTO Customers (id, name) VALUES
(1, 'Peter'),
(2, 'Simon'),
(3, 'Mary');

Answer 2

我认为你正在寻找这个：

declare @myStart int
declare @myEnd int
SET @myStart = 11
SET @myEnd = 14

SELECT c.name
FROM Customers c
INNER JOIN Holidays h
    ON c.id=h.customer_id
WHERE
(@myStart BETWEEN h.start AND h.end) OR
(@myEnd BETWEEN h.start AND h.end) OR
(@myStart < h.start AND @myEnd > h.end)

Answer 3

你可以这样做

  -- Get customers only from Customers table
  SELECT name FROM Customers 
  WHERE id NOT IN ( -- Get the intersection between the two tables
                    SELECT id FROM Customers JOIN 
                    Holidays ON Customers.Id = Holidays.customer_id
                    WHERE Holidays.start=12 AND Holidays.end = 12)

Answer 4

我不认为您想“删除”任何内容，只需选择与您的开始/结束值重叠的值，对吗？试试这个

SELECT
    Name
FROM
    Customers c
    JOIN Holidays h on h.Customer_id = c.ID 
WHERE
    Start >= @Start
    OR End <= @End

Answer 5

select
    c.name
from
    Customers c
    left outer join
        Holidays h
    on
        h.customer_id=c.id
where
    h.start <= 11
    and
    h.end >= 14
group by
    c.id

如何进行删除值的连接？

5 个答案: