I need to do a join using a JOIN TABLE ON ... AND ... using Spring Data JPA criteria builder.
I know I can do a basic join like so:
Join<ReportEntity, ProductEntity> productJoin = root.join("products", JoinType.LEFT);
But can I specify extra criteria for the join? If not, is there another way to achieve this using the Criteria Builder? This is the SQL query I'd like to reproduce:
SELECT r.id, p.rare
FROM REPORT r
LEFT JOIN PRODUCT p
ON r.id = p.report_id AND p.rare = 1
WHERE p.report_id IS NULL;
Note that specifying p.rare = 1 in the above query in the WHERE clause does not give the desired result, it needs to go in the ON clause.
Join<ReportEntity, ProductEntity> productJoin = root.join("products", JoinType.LEFT);
Predicate joinPredicate = criteriaBuilder.equal(root.get("id"), productJoin.get("reportId"));
Predicate rarePredicate = criteriaBuilder.equal(productJoin.get("rare"), 1);
productJoin.on(joinPredicate, rarePredicate);
Related
My title is probably not very clear, so I made a little schema to explain what I'm trying to achieve. The xxxx_uid labels are foreign keys linking two tables.
Goal: Retrieve a column from the grids table by giving a proj_uid value.
I'm not very good with SQL joins and I don't know how to build a single query that will achieve that.
Actually, I'm doing 3 queries to perform the operation:
1) This gives me a res_uid to work with:
select res_uid from results where results.proj_uid = VALUE order by res_uid asc limit 1"
2) This gives me a rec_uid to work with:
select rec_uid from receptor_results
inner join results on results.res_uid = receptor_results.res_uid
where receptor_results.res_uid = res_uid_VALUE order by rec_uid asc limit 1
3) Get the grid column I want from the grids table:
select grid_name from grids
inner join receptors on receptors.grid_uid = grids.grid_uid
where receptors.rec_uid = rec_uid_VALUE;
Is it possible to perform a single SQL that will give me the same results the 3 I'm actually doing ?
You're not limited to one JOIN in a query:
select grids.grid_name
from grids
inner join receptors
on receptors.grid_uid = grids.grid_uid
inner join receptor_results
on receptor_results.rec_uid = receptors.rec_uid
inner join results
on results.res_uid = receptor_results.res_uid
where results.proj_uid = VALUE;
select g.grid_name
from results r
join resceptor_results rr on r.res_uid = rr.res_uid
join receptors rec on rec.rec_uid = rr.rec_uid
join grids g on g.grid_uid = rec.grid_uid
where r.proj_uid = VALUE
a small note about names, typically in sql the table is named for a single item not the group. thus "result" not "results" and "receptor" not "receptors" etc. As you work with sql this will make sense and names like you have will seem strange. Also, one less character to type!
Im trying to match this SQL query in querydsl
SELECT tr.* FROM test.TRIP_REQ tr left outer join test.ADDR_BOOK ab on tr.REQ_USERID=ab.USER_ID
I know how to make left join query if you join into identity column but struggle to make it work with joining on 2 alternative columns. tr.REQ_USERID and ab.USER_ID are not identity columns
This is my querydsl:
QTripReq qTripReq = QTripReq.tripReq;
QAddressBook qABook = QAddressBook.addressBook;
JPAQuery query = new JPAQuery(entityManager);
query.from(qTripReq).leftJoin(qABook).on(qTripReq.requestorUser.id.eq(qABook.user.id)).list(qTripReq);
This throws error:
Path expected for join! [select tripReq from com.TripReq tripReq left join ADDR_BOOK addressBook with tripReq.requestorUser.id = addressBook.user.id where tripReq.assignedCompany.id = ?1]
You need to add a target entity path to leftJoin(), so that
QTripReq qTripReq = QTripReq.tripReq;
QAddressBook qABook = QAddressBook.addressBook;
JPAQuery query = new JPAQuery(entityManager);
query.from(qTripReq).leftJoin(qTripReq.addressBook, qABook).on(qTripReq.requestorUser.id.eq(qABook.user.id)).list(qTripReq);
Take a look on Using joins section in docs.
I'm trying to retrieve a list of components via my computer_system, BUT if a computer system's graphics card is set to null (I.e. It has an onboard), the row isn't returned by my select statement.
I've been trying to use COALESCE without results. I've also tried with and OR in my WHERE clause, which then just returns my computer system with all different kinds of graphic cards.
Relevant code:
SELECT
computer_system.cs_id,
computer_system.cs_name,
motherboard.name,
motherboard.price,
cpu.name,
cpu.price,
gfx.name,
gfx.price
FROM
public.computer_case ,
public.computer_system,
public.cpu,
public.gfx,
public.motherboard,
public.ram
WHERE
computer_system.cs_ram = ram.ram_id AND
computer_system.cs_cpu = cpu.cpu_id AND
computer_system.cs_mb = motherboard.mb_id AND
computer_system.cs_case = computer_case.case_id AND
computer_system.cs_gfx = gfx.gfx_id; <-- ( OR computer_system.cs_gfx IS NULL)
Returns:
1;"Computer1";"Fractal Design"; 721.00; "MSI Z87"; 982.00; "Core i7 I7-4770K "; 2147.00; "Crucial Gamer"; 1253.00; "ASUS GTX780";3328.00
Should I use Joins? Is there no easy way to say return the requested row, even if there's a bloody NULL value. Been struggling with this for at least 2 hours.
Tables will be posted if needed.
EDIT: It should return a second row:
2;"Computer2";"Fractal Design"; 721.00; "MSI Z87"; 982.00; "Core i7 I7-4770K "; 2147.00; "Crucial Gamer"; 1253.00; "null/nothing";null/nothing
You want a LEFT OUTER JOIN.
First, clean up your code so you use ANSI joins so it's readable:
SELECT
computer_system.cs_id,
computer_system.cs_name,
motherboard.name,
motherboard.price,
cpu.name,
cpu.price,
gfx.name,
gfx.price
FROM
public.computer_system
INNER JOIN public.computer_case ON computer_system.cs_case = computer_case.case_id
INNER JOIN public.cpu ON computer_system.cs_cpu = cpu.cpu_id
INNER JOIN public.gfx ON computer_system.cs_gfx = gfx.gfx_id
INNER JOIN public.motherboard ON computer_system.cs_mb = motherboard.mb_id
INNER JOIN public.ram ON computer_system.cs_ram = ram.ram_id;
Then change the INNER JOIN on public.gfx to a LEFT OUTER JOIN:
LEFT OUTER JOIN public.gfx ON computer_system.cs_gfx = gfx.gfx_id
See PostgreSQL tutorial - joins.
I very strongly recommend reading an introductory tutorial to SQL - at least the PostgreSQL tutorial, preferably some more material as well.
It looks like it's just a bracket placement issue. Pull the null check and the graphics card id comparison into a clause by itself.
...
computer_system.cs_case = computer_case.case_id AND
(computer_system.cs_gfx IS NULL OR computer_system.cs_gfx = gfx.gfx_id)
Additionally, you ask if you should use joins. You are in fact using joins, by virtue of having multiple tables in your FROM clause and specifying the join criteria in the WHERE clause. Changing this to use the JOIN ON syntax might be a little easier to read:
FROM sometable A
JOIN someothertable B
ON A.somefield = B.somefield
JOIN somethirdtable C
ON A.somefield = C.somefield
etc
Edit:
You also likely want to make the join where you expect the null value to be a left outer join:
SELECT * FROM
first_table a
LEFT OUTER JOIN second_table b
ON a.someValue = b.someValue
If there is no match in the join, the row from the left side will still be returned.
I have a question about joins in NHIBERNATE. We had an issue with our sql query that was generated but nhibernate. Our db developer optimized the raw sql so it works as we need, but we need to change the nhibernate code to make generated sql look like optimized.
the part of the original part of the query is:
FROM PERSON_VISIT this_
inner join PERSON_Basic per2_
on this_.PERSON_ID = per2_.PERSON_ID
left outer join PERSONC_QUESTIONS perint10_
on per2_.PERSON_ID = perint10_.PERSON_ID
left outer join TELEPHONE_QUESTIONS intaudit13_
on perint10_.PP_QUESTIONS_ID = intaudit13_.PP_QUESTIONS_ID
inner join C_QUESTIONS intdef14_
on perint10_.QUESTION_ID = intdef14_.QUESTION_ID
and perint10_.QUESTIONS_CODE = intdef14_.QUESTIONS_CODE
and perint10_.QUESTION_ID = intdef14_.QUESTION_ID
The optimized one is :
FROM PERSON_VISIT this_
inner join PERSON_Basic per2_
on this_.PERSON_ID = per2_.PERSON_ID
left outer join PERSONC_QUESTIONS perint10_
on per2_.PERSON_ID = perint10_.PERSON_ID
left outer join TELEPHONE_QUESTIONS intaudit13_
on perint10_.PP_QUESTIONS_ID = intaudit13_.PP_QUESTIONS_ID
left outer join C_QUESTIONS intdef14_
on perint10_.QUESTION_ID = intdef14_.QUESTION_ID
and perint10_.QUESTIONS_CODE = intdef14_.QUESTIONS_CODE
and perint10_.QUESTION_ID = intdef14_.QUESTION_ID
and intdef14_.DISCIPLINE_CODE = this_.DISCIPLINE_CODE
To change query from inner join to left outer join is easy, i changed only one line of code:
.CreateAlias("PersonInt.QuestionEntity", "IntDef", JoinType.LeftOuterJoin)
But how I can add
and intdef14_.DISCIPLINE_CODE = this_.DISCIPLINE_CODE
using nhibernate code?
There is an option to add reference from PERSON_VISIT definition to C_QUESTIONS, but the problem is that
PERSON_VISIT is used everywhere and I don't want this change to possibly break other queries, I just wnat to add only one line of code to add, how I can do that? Is there any way to have access to the raw join to change it? Or some other way to add this
and intdef14_.DISCIPLINE_CODE = this_.DISCIPLINE_CODE
To the query?
I know that somebody will say that we can add a restriction to the query through criteria.Add, but it is not an option cause db developer optimized our query taking this restriction from WHERE clause to the join.
How I can do that quickly without changing the models definitions? Just changing only this one query without changing the whole model?
It is possible using HQL and the Criteria API's.
This question gives you the answer: Adding conditionals to outer joins with nhibernate
Something like this may solve your issue.
.CreateAlias("PersonInt.QuestionEntity", "IntDef", JoinType.LeftOuterJoin,
Restrictions.EqProperty("DISCIPLINE_CODE", "IntDef.DISCIPLINE_CODE"))
Thanks for answers. We use 2.0 version of NHibernate in our project so we didn't have a chance to use new methods of .CreateAlias with restrictions.
I have fixed an issue using Interceptors:
public class SqlInterceptor : EmptyInterceptor, IInterceptor
{
SqlString IInterceptor.OnPrepareStatement(SqlString sql)
{
//manipulating with the sql
return sql;
}
}
than
var factory = Session.SessionFactory;
var session = factory.OpenSession(new SqlInterceptor());
And use my query without a change.
I've been reading Hibernate documentation, but I haven't found anything that would explain how to do the following.
I have the following SQL code that I'm trying to convert to HQL:
SELECT {msg.*}, {cmd.*}
FROM Schema.Messages AS msg
LEFT OUTER JOIN schema.send_commands AS cmd
ON cmd.message_key = msg.unique_key
AND ( lower(cmd.status) IN (lower('failed') ) )
WHERE msg.sequence_received < 10";
The mainissue I'm having is that I'm unable to have two clauses on a LEFT OUTER JOIN. HQL allows me to have
ON cmd.message_key = msg.unique_key
, but how do I add the
AND clause 2?
You can add extra join conditions using with keyword, something like this (depends on your mapping):
SELECT m, c
FROM Message m LEFT JOIN m.commands c WITH (lower(c.status) = 'failed')
WHERE m.sequenceReceived < 10
See also:
16.3. Associations and joins