Question

我想在我的数据库中获取每个预订的第一个日期。

表BOOKINGS就像：

id | id_client_booking | the_date

表CLIENT_BOOKINGS是

id | etc | etc

<{1>} BOOKINGS每个id_client_booking对应id CLIENT_BOOKINGS个

SELECT
min(the_date) AS start_date, id_client_booking
FROM `day_bookings`AS db
LEFT JOIN `client_bookings`AS cb ON db.id_client_booking = cb.id

，并且可以有很多日期。

我希望获取每位客户预订的第一个日期。这个选择只给我所有客户预订的第一个日期。我错过了什么？

SELECT
min(the_date) AS db.start_date, db.id_client_booking
                 ^^             ^^
FROM `day_bookings`AS db
LEFT JOIN `client_bookings`AS cb ON db.id_client_booking = cb.id

也试过：

You have an error in your SQL syntax;

但错误：{{1}}

Answer 1

你错过了GROUP BY，试试这个：

SELECT MIN(the_date) AS start_date, id_client_booking
FROM `day_bookings`AS db
LEFT JOIN `client_bookings`AS cb 
ON db.id_client_booking = cb.id
GROUP BY id_client_booking

Answer 2

您需要使用GROUP BY汇总功能才能使MIN()正常工作

SELECT min(the_date) AS start_date, id_client_booking
FROM `day_bookings` AS db
LEFT JOIN `client_bookings` AS cb 
ON db.id_client_booking = cb.id
GROUP BY db.id_client_booking

Answer 3

您只能使用AS关键字来定义表达式或别名的名称您不能使用它直接指向列。因此是语法错误。

SELECT
min(the_date) AS db.start_date, db.id_client_booking
                 ^^             ^^
FROM `day_bookings`AS db
LEFT JOIN `client_bookings`AS cb ON db.id_client_booking = cb.id

应该是：

SELECT
min(the_date) AS 'start_date', db.id_client_booking
FROM `day_bookings`AS db
LEFT JOIN `client_bookings`AS cb ON db.id_client_booking = cb.id

离开加入获得最小日期

3 个答案: