左加入以获得分钟日期

Question

I want to get the first date of each booking in my database.

Table BOOKINGS is like:

id | id_client_booking | the_date

Table CLIENT_BOOKINGS is

id | etc | etc

on BOOKINGS each id_client_booking correponds to one id of CLIENT_BOOKINGS , and can have many dates.

I would like to get the first date of each client booking. This select gives me just the first date of all client bookings. What am I missing?

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

Tried also:

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

but that gave error: You have an error in your SQL syntax;

Answer 1

You are missing a GROUP BY , try this:

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

You need to use GROUP BY aggregate function to make MIN() works

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

You can only use AS key word to define names for expressions or aliases.
You can't use it to point to a column directly. And hence is the syntax error.

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

It should be:

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