I wrote the following query for MySQL:
SELECT subquery.t1_column1,
subquery.t2_id,
MAX(subquery.val)
FROM (
SELECT t1.column1 as t1_column1,
t1.id_t2 AS t2_id,
count(1) AS val
FROM table1 t1
INNER JOIN table2 t2
ON t2.id = t1.id_t2
GROUP BY t1.id_t2
) subquery
GROUP BY t1_column1
And I'd like to translate it into JPA (JPQL or criteria query).
I don't know how to make this max(count) thing, and JPA doesn't seem to like the SELECT FROM SELECT...
If anyone has an idea other than native queries (I'll do it for now), it would be great.
I haven't checked tha JPA specification, but given that the Hibernate documentation says
Note that HQL subqueries can occur only in the select or where
clauses.
I very much doubt that your query can be transformed in a valid JPQL query.
You'll have to keep using this native SQL query.
JPA 2.0 JPQL does not support sub-selects in the from clause. You may want to try to rewrite your query, or use a native SQL query.
EclipseLink 2.4 will support sub-selects in the FROM clause,
see,
http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Querying/JPQL#Sub-selects_in_FROM_clause
Related
I have native query like this
SELECT sample.api_name,
sample.hitcount,
r.unit_rate*sample.hitcount AS amnt
FROM
(SELECT u.api_name AS api_name,u.tenant_id,
u.count AS hitcount
FROM tableA u
WHERE u.tenant_id = :tenant
AND u.time_stamp BETWEEN :dateFrom AND :dateTo
GROUP BY u.api_name,
u.tenant_id) AS sample
LEFT JOIN tableB r ON sample.api_name = r.api_name
AND sample.tenant_id =r.tenant_id
The values "tenant,dateFrom,dateTo" values are providing by using #Param tag.
I have tried to convert to the jpql query in spring data jpa.
But by seeing in some reference documents i came to know that the
Jpql inner queries are not supported in the FROM clause.
is that my point correct or not. If not Please help me to write in JPQL if my point is correct please help to write in Criteria api.
I need to implement select from a nested query, for the sake of simplicity let it be:
select * from (select * from city) c
How can this be done using CriteriaQuery and Subquery?
You can't because (select * from city) is not an entity and CritieriaAPI queries on entities not on tables.
The only way would be to create a view for (select * from city) and map that view to an entity.
First, your syntax is not JPA compliant as mentioned previously, secondly, you must know that subqueries in JPQL are allowed only in WHERE and HAVING clauses. The same applies to Criteria queries. If you need the more powerful SQL subquery features then with JPA you have to use JPA provisions for native queries, or otherwise, use another type of JDBC library.
Spring DATA JPA support subquery in from ?
like
select * from (
select unique_id
from table_a
) as from_a
inner join table_b
on from_a.unique_id = table_b.unique_id
querydsl JPASubquery or Spring DATA criteria impossible?
I think it is noe possible.
in other way. you use JPAExpressions. it will be serching for subquery in query dsl.
But i aleardy user that subQuery that are result only one table.
Is there a way to do an ordering in JPQL query like:
SELECT v
FROM Vehicle v
WHERE ...
ORDER BY v.lastUserUpdate DESC NULLS LAST, v.id DESC;
The NULLS LAST breaks the query. Is there a correct way to do this?
I don't know a JPQL function to allow this as I believe it is database specific. JPA 2.0 has a 'SQL' key word that you can use to have "nulls last" passed through. Something like
"ORDER BY v.lastUserUpdate DESC SQL('NULLS LAST'), ..."
See
http://java-persistence-performance.blogspot.ca/2012/05/jpql-vs-sql-have-both-with-eclipselink.html for more details on what is available in JPA and eclipselink. TopLink uses EclipsLink for JPA, so you will have to verify the version you are using and use native TopLink API if it doesn't support it and you can't upgrade.
I've written a JPQL statement that unions multiple select statements, each of which selects a different string constant. A simplified version of the query would look something like this:
SELECT DISTINCT 'A' AS widget_type
FROM WidgetA widgetA
WHERE widgetA.creationTimestamp > :cutoff
UNION SELECT DISTINCT 'B' AS widget_type
FROM WidgetB widgetB
WHERE widgetB.creationTimestamp > :cutoff
The query doesn't cause any errors but I'm not getting the result I expect. I see that the generated SQL doesn't have any unions - it only queries the table from the first select:
select distinct 'A' as col_0_0_
from widget_a widget0_
where widget0_.creation_timestamp>?
Is there an obvious reason why JPA would disregard everything after the first select statement? If it makes any difference, I am using Hibernate 4.1.9 as the JPA implementation, with a MySQL database.
JPQL has no such concept as UNION. So consequently any "query" that has it is not JPQL and so ought to be rejected as invalid JPQL (which DataNucleus JPA certainly would do)