I am trying to do a LEFT JOIN in Hibernate Query Language, in MySQL I can do this as follows:
select * from day_timetable_timeslots t LEFT JOIN golfnine_date_time_entity d ON d.start_time = t.start_time
In my table day_timetable_timeslots I have many time intervals for the whole day with 15 minute increments. eg. 00:00:00, 00:15:00, 00:30:00, ... to end of day. So it shows me all the time intervals with any matching golfnine_date_time_entity, but I cannot seem to work out how to do this in Hibernate Query Language.
Well I can do the LEFT JOIN by the following HQL.
select o.id, book.id from DayTimetableTimeslots o left outer join o.bookings book where o.id > 0
I don't know why I must put the o.id > 0 there, but it works.
However, I want to only select book.id's where the booking has a where condition. I tried:
select o.id, book.id from DayTimetableTimeslots o left outer join o.bookings book where o.id > 0 and book.dateTime.startDate > '2010-01-01'
But this doesn't work correctly, it shows only some of the DayTimetableTimeslots, but not all of them, as it is supposed to do so.
I basically want to do this mysql query in HQL.
select t.id as start_time_sequence, t.start_time as all_start_time, d.* from day_timetable_timeslots t LEFT JOIN golfnine_date_time_entity d ON d.start_time = t.start_time AND t.customer_id = d.customer_id AND d.start_date = '2010-01-24' WHERE t.customer_id = 11
Thanks, Philip
In mysql I can do the following and it shows me all bookings against their start time. All start times are stored in day_timetable_timeslots.
select t.start_time, d.id from day_timetable_timeslots t LEFT JOIN golfnine_date_time_entity d ON d.start_time = t.start_time
'00:00:00', NULL
'00:15:00', NULL
'00:30:00', NULL
'00:45:00', NULL
'01:00:00', '443'
'01:15:00', NULL
'01:30:00', NULL
'01:45:00', NULL
'02:00:00', '444'
... for the whole day, it matches up the ids of the golfnine_date_time_entity with the times in day_timetable_timeslots.
The good thing about this mysql query is I can set some criteria on the booking, eg.
select t.id, t.start_time, d.id from day_timetable_timeslots t LEFT JOIN golfnine_date_time_entity d ON d.start_time = t.start_time AND t.customer_id = d.customer_id AND d.start_date = '2010-01-24' WHERE t.customer_id = 11
I get
... lots of data then
'31', '07:15:00', NULL
'32', '07:30:00', NULL
'33', '07:45:00', NULL
'34', '08:00:00', '501'
'35', '08:15:00', NULL
'36', '08:30:00', NULL
'37', '08:45:00', NULL
'38', '09:00:00', NULL
'39', '09:15:00', NULL
... lots more data
So its only showing the booking on that date specified and the customer id.
Its so hard to do this in HQL...
This is the join I want in HQL.
select o.id, b.id from DayTimetableTimeslots o, LegacyDateTimeEntity b where b.customer.id = 11 and b.startDate = '2010-02-07' and o.startTime = b.startTime
Gives this SQL.
select
daytimetab0_.id as col_0_0_,
legacydate1_.id as col_1_0_
from
day_timetable_timeslots daytimetab0_,
golfnine_date_time_entity legacydate1_
where
legacydate1_.customer_id=11
and legacydate1_.start_date='2010-02-07'
and daytimetab0_.start_time=legacydate1_.start_time
But - it only returns 1 row because only one golfnine_date_time_entity matches, I want all of the day_timetable_timeslots rows returned.
So I tried in HQL.
select o.id, o.bookings.size from DayTimetableTimeslots o left join o.bookings book left join book.dateTime dt with dt.customer.id = 11 and dt.startDate = '2010-02-29' where 1 = 1
Which sadly seems to ignore the with expression.
It returns this SQL.
select
daytimetab0_.id as col_0_0_,
(select
count(bookings3_.timeslot_id)
from
golfnine_booking bookings3_
where
daytimetab0_.id=bookings3_.timeslot_id) as col_1_0_
from
day_timetable_timeslots daytimetab0_
left outer join
golfnine_booking bookings1_
on daytimetab0_.id=bookings1_.timeslot_id
left outer join
golfnine_date_time_entity legacydate2_
on bookings1_.date_time_id=legacydate2_.id
and (
legacydate2_.customer_id=11
and legacydate2_.start_date='2010-02-29'
)
where
1=1
Which just joins all matching relationships between tables and ignores legacydate2_.customer_id=11 and legacydate2_.start_date='2010-02-29'
I found that this seems to work. Note I am referencing dt2 which is in the with clause.
select distinct o.startTime, dt2.id, book.uniqueDateTimeResource from DayTimetableTimeslots o left join o.bookings book with book.deleted = 0 left join book.dateTime dt2 with dt2.startDate = '2010-01-19' and dt2.deleted = 0
The Left Join is a keyword in SQL, which returns all data from the left-hand side table and matching records from the right-hand side table. We can see the NULL values from the right side if there is no match. We can apply the Joins in Hibernate by using the HQL query or native SQL query.
We can see the NULL values from the right side if there is no match. We can apply the Joins in Hibernate by using the HQL query or native SQL query. To make a join between the two tables, the two tables must be in a logical relationship.
Hibernate - Query Language. Hibernate Query Language (HQL) is an object-oriented query language, similar to SQL, but instead of operating on tables and columns, HQL works with persistent objects and their properties. HQL queries are translated by Hibernate into conventional SQL queries, which in turns perform action on database.
Hibernate List Query Example Note that in HQL, we can omit the SELECT keyword and just use the FROM instead. 3. Hibernate Search Query Example The cool thing here is Hibernate automatically generates JOIN query between the Product and Category tables behind the scene. Thus we don’t have to use explicit JOIN keyword: 4.
I can think of two potential problems that you are running into:
You are having issues with date/time precision between your java and SQL code. You can try adjusting the date by a small increment, and see if the correct values show up.
Your hibernate mapping is not correct. It looks like you always join on multiple columns? Your schema is a little bit confusing to me. Do you use the @JoinColumns annotation to specify multiple columns in your association (if you're using annotations), or the equivalent in the XML mapping file?
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