Join with subquery in Querydsl SQL 3.7.4

[Paul Woolley]

Hi,

There's some SQL that I'd like to express using Querydsl SQL 3.7.4.  It involves having a subquery in both the from and the join parts of the SQL.  Like this...

select fields

from (

select fields

from some table

where some restrictions

) t1

full join (

select fields

from some other table

where some restrictions

) t2

on 

join conditions

I've done some searching within this group and stackoverflow and can see that joins on subqueries are not allowed with Querydsl JPA, and that there is some way to do this in Querydsl 4 using SQLExpressions.select, but I haven't found a definitive answer yet as to whether joining with a subquery is possible in Querydsl SQL 3.7.4.

Here is a contrived code example of what I was hoping to do with Querydsl:

SQLSubQuery main = new SQLSubQuery();

SQLSubQuery fromSubQuery = new SQLSubQuery().from().where();

SQLSubQuery joinSubQuery = new SQLSubQuery().from().where();

BooleanExpression joinConditions = BooleanTemplate.TRUE;

main.from(fromSubQuery.list(SQLExpressions.all))

.join(joinSubQuery.list(SQLExpressions.all)) // <-- This part does not compile

.on(joinConditions)

.list(SQLExpressions.all);

For reasons, upgrading to version 4 is not an option and the "main" must be an instance of SQLSubQuery also.

My experimentation so far is strongly suggesting that this is not possible, but if someone knows how to achieve this, then it is greatly appreciated.

Thank you,

  Paul.