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How to get result set by checking a specific element in an aggregated array using JOOQ?

I want to filter results by a specific value in the aggregated array in the query.
Here is a little description of the problem.
Section belongs to the garden. Garden belongs to District and District belongs to the province.
Users have multiple sections. Those sections belong to their gardens and they are to their Districts and them to Province.
I want to get user ids that have value 2 in district array.
I tried to use any operator but it doesn't work properly. (syntax error)
Any help would be appreciated.
ps: This is possible writing using plain SQL
rs = dslContext.select(
field("user_id"),
field("gardens_array"),
field("province_array"),
field("district_array"))
.from(table(select(
arrayAggDistinct(field("garden")).as("gardens_array"),
arrayAggDistinct(field("province")).as("province_array"),
arrayAggDistinct(field("distict")).as("district_array"))
.from(table("lst.user"))
.leftJoin(table(select(
field("section.user_id").as("user_id"),
field("garden.garden").as("garden"),
field("garden.province").as("province"),
field("garden.distict").as("distict"))
.from(table("lst.section"))
.leftJoin("lst.garden")
.on(field("section.garden").eq(field("garden.garden")))
.leftJoin("lst.district")
.on(field("district.district").eq(field("garden.district")))).as("lo"))
.on(field("user.user_id").eq(field("lo.user_id")))
.groupBy(field("user.user_id"))).as("joined_table"))
.where(val(2).equal(DSL.any("district_array"))
.fetch()
.intoResultSet();

Your code is calling DSL.any(T...), which corresponds to the expression any(?) in PostgreSQL, where the bind value is a String[] in your case. But you don't want "district_array" to be a bind value, you want it to be a column reference. So, either, you assign your arrayAggDistinct() expression to a local variable and reuse that, or you re-use your field("district_array") expression or replicate it:
val(2).equal(DSL.any(field("district_array", Integer[].class)))
Notice that it's usually a good idea to be explicit about data types (e.g. Integer[].class) when working with the plain SQL templating API, or even better, use the code generator.

Mapping partial column values using Toplink

Suppose I have a list of IDs as follows:
EmployeeID
-------
ABCD
AECD
ABDF
ACDF
ACDE
I have a need to read the distinct values from a list of codes, while selecting only the first two characters of the column.
In other words, its similar to using the following query:
SELECT DISTINCT LEFT (EmployeeID,2) FROM TABLE1
My question is how do I map such a field in TOPLINK.
Note:I have created a class for the EmployeeID, but dont have an idea of mapping a partial field.

Ok... After looking at many workarounds, I seem to have a more suited solution.
I created an object for this particular scenario (the POJO has only the field for the holding the 2 Char ID, and its getter and setter methods).
During the mapping, I mapped the above field to the DB column in question (EmployeeID in the table described above).
Now I selected "Custom Queries" for the above object and entered the following query for "Read all" tab.
SELECT DISTINCT LEFT (EmployeeID,2) AS EmploeeID FROM TABLE1
All the read all operations on the object will now return the list of distinct first 2 characters of IDs.
Welcome anyone's opinion on this.

Better to query once, then organize objects based on returned column value, or query twice with different conditions?

I have a table which I need to query, then organize the returned objects into two different lists based on a column value. I can either query the table once, retrieving the column by which I would differentiate the objects and arrange them by looping through the result set, or I can query twice with two different conditions and avoid the sorting process. Which method is generally better practice?
MY_TABLE
NAME AGE TYPE
John 25 A
Sarah 30 B
Rick 22 A
Susan 43 B
Either SELECT * FROM MY_TABLE, then sort in code based on returned types, or
SELECT NAME, AGE FROM MY_TABLE WHERE TYPE = 'A' followed by
SELECT NAME, AGE FROM MY_TABLE WHERE TYPE = 'B'

Logically, a DB query from a Java code will be more expensive than a loop within the code because querying the DB involves several steps such as connecting to DB, creating the SQL query, firing the query and getting the results back.
Besides, something can go wrong between firing the first and second query.
With an optimized single query and looping with the code, you can save a lot of time than firing two queries.
In your case, you can sort in the query itself if it helps:
SELECT * FROM MY_TABLE ORDER BY TYPE
In future if there are more types added to your table, you need not fire an additional query to retrieve it.

It is heavily dependant on the context. If each list is really huge, I would let the database to the hard part of the job with 2 queries. At the opposite, in a web application using a farm of application servers and a central database I would use one single query.
For the general use case, IMHO, I will save database resource because it is a current point of congestion and use only only query.
The only objective argument I can find is that the splitting of the list occurs in memory with a hyper simple algorithm and in a single JVM, where each query requires a bit of initialization and may involve disk access or loading of index pages.

In general, one query performs better.
Also, with issuing two queries you can potentially get inconsistent results (which may be fixed with higher transaction isolation level though ).
In any case I believe you still need to iterate through resultset (either directly or by using framework's methods that return collections).

From the database point of view, you optimally have exactly one statement that fetches exactly everything you need and nothing else. Therefore, your first option is better. But don't generalize that answer in way that makes you query more data than needed. It's a common mistake for beginners to select all rows from a table (no where clause) and do the filtering in code instead of letting the database do its job.

It also depends on your dataset volume, for instance if you have a large data set, doing a select * without any condition might take some time, but if you have an index on your 'TYPE' column, then adding a where clause will reduce the time taken to execute the query. If you are dealing with a small data set, then doing a select * followed with your logic in the java code is a better approach

There are four main bottlenecks involved in querying a database.
The query itself - how long the query takes to execute on the server depends on indexes, table sizes etc.
The data volume of the results - there could be hundreds of columns or huge fields and all this data must be serialised and transported across the network to your client.
The processing of the data - java must walk the query results gathering the data it wants.
Maintaining the query - it takes manpower to maintain queries, simple ones cost little but complex ones can be a nightmare.
By careful consideration it should be possible to work out a balance between all four of these factors - it is unlikely that you will get the right answer without doing so.

You can query by two conditions:
SELECT * FROM MY_TABLE WHERE TYPE = 'A' OR TYPE = 'B'
This will do both for you at once, and if you want them sorted, you could do the same, but just add an order by keyword:
SELECT * FROM MY_TABLE WHERE TYPE = 'A' OR TYPE = 'B' ORDER BY TYPE ASC
This will sort the results by type, in ascending order.
EDIT:
I didn't notice that originally you wanted two different lists. In that case, you could just do this query, and then find the index where the type changes from 'A' to 'B' and copy the data into two arrays.

Order by a temporary column computed using case when

I have 2 entities Book and BookProperty in a one-to-many relationship. I need to retrieve books sorted by upload_date, english language books coming first using JPA Criteria with pagination and stuff (JPQL/native sql is not an option).
This is what the native query for this operation would look like (postgres):
select distinct
b.book_id,
b.name, b.author, ... ,
b.upload_date,
case when p.property_name='language' and lower(p.property_value)='english'
then 0 else 1 end as book_language,
from books b
left outer join book_properties p
on b.book_id=p.book_id
order by book_language asc, b.upload_date desc;
The problem is that I can't get the 'case' part to be selected via criteria API and sort by it. I know that it is possible via a multiselect and a tuple but I would like to avoid that, because really I do not need this column in the application. I would like to just retrieve sorted Book objects and not tuples of (Book, Integer).
I tried to move the case part into the order by and managed to compute the query via JPA Criteria, but in that case setDistinct(true) resulted in an error, because all columns in order by must be part of distinct. So moving the case part to order doesn't look like an option.
Please help me implement this query using JPA Criteria, preferably without using tuples or wrapper objects, but that will do as well if there are no other options.

Queryproblem with mongodb

I have 2 collections in a mongodb database.
example:
employee(collection)
_id
name
gender
homelocation (double[] indexed as geodata)
companies_worked_in (reference, list of companies)
companies(collection)
_id
name
...
Now I need to query all companies who's name start with "wha" and has/had employees which live near (13.444519, 52.512878) ie.
How do I do that without taking too long?
With SQL it would've been a simple join (without the geospatiol search of course... :( )

You can issue 2 queries. (Queries I wrote are in JavaScript)
First query extracts all companies whose name starts with wha.
db.companies.find({name: {$regex: "^wha"}}, {_id: 1})
Second query can be like
db.employees.find({homelocation: {$near: [x,y]}, companies_worked_in: {$in: [result_from_above_query]} }, {companies_worked_in: 1})
Now simply filter companies_worked_in and have only those companies whose name starts with wha. I know it seems like the first query is useless in this case. But a lot of records would be filtered by $in query.
You might have to write some intermediate code between this two queries. I know this is not a single query solution. But this is one possible way to go and performance is also good depending upon what fields you index upon. In this case consider creating index on name (companies collection) and homelocation (geo-index) + companies_worked_in (employee collection) would help you gain performance.
P.S.
I doubt if you could create a composite index over homelocation and companies_worked_in, since both are arrays. You would have to index on one of these fields only. You might not be able to have a composite index.
Suggestion
Store the company name as well in employee collection. That ways you can avoid first query.