Question

我想使用SELECT参数作为第一个查询输出进行多个WHERE查询

SELECT id FROM hotel where group_id != 1;

输出：1,3,4,5,6,7,9

现在，我想获取这些ID（第一个查询的输出）并对其进行多个SELECT

SELECT user_id FROM users where hotel_id = [1,3,4,5,6,7,9];

Answer 1

您可以使用IN（带有子查询）而不是=使用以下解决方案：

-- ignore hotel_id with NULL using IN with sub-select
SELECT user_id 
FROM users 
WHERE hotel_id IN (
    SELECT id 
    FROM hotel 
    WHERE group_id <> 1
);

-- with hotel_id NULL using IN with sub-select
SELECT user_id 
FROM users 
WHERE hotel_id IN (
    SELECT id 
    FROM hotel 
    WHERE group_id <> 1
) OR hotel_id IS NULL;

另一个解决方案可以是使用INNER JOIN或LEFT JOIN的以下解决方案：

-- ignore hotel_id with NULL using INNER JOIN
SELECT users.user_id
FROM users INNER JOIN hotel ON users.hotel_id = hotel.id 
WHERE hotel.group_id <> 1

-- with hotel_id NULL using LEFT JOIN
SELECT users.user_id
FROM users LEFT JOIN hotel ON users.hotel_id = hotel.id
WHERE hotel.group_id <> 1 OR users.hotel_id IS NULL;

demo on dbfiddle.uk

如何使用SQL查询输出

1 个答案: