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From "Durchholz, Joachim" <Joachim.Durchh...@hennig-fahrzeugteile.de>
Subject RE: SelectQuery + Orderings
Date Mon, 30 Jan 2012 10:12:05 GMT
+1 on using a chained query builder similar to that for Ruby/Rails.

> Am I the only one that finds andQualifier(Expression),
> orQualifier(Expression), setQualifier(Expression),
> and Expression getQualifier() to be odd?

As an application developer, I'd find either far too verbose. I want something where I know
from context what I'm talking about, because I'm typically writing a heap of conditions, so
it's enough to write it once.

E.g. it could be
  new QualifierList ()
  .like("name", "b%")
  .or (new QualifierList ()
    .greater("age", 23)
    .less("age", 27)
  )

The QualifierList constructor and the first qualifier can be merged into one if writing a
small subclass of QualifierList is in order:
  class Greater extends QualifierList {
    Greater(String property, int value) {
      super ();
      this.greater(property, value);
    }
  }
giving
  new QualifierList ()
  .like("name", "b%")
  .or (
    new Greater("age", 23)
    .less("age", 27)
  )

The same technique could be applied to Aristedes' example:

  SelectQuery(Artist.class)
  .like("name", "b%")
  .or (
    new Greater("age", 23)
    .less("age", 27)
  )
  .join(Gallery.class)
  .limit(10)
  .order(Artist.name)
  .perform()

.like, .or, .greater, .less would then delegate to SelectQuery's member
  QualifierList whereConditions
(which would need to be merged using AND when generating SQL)


Note that these are still Expressions, not Qualifiers, since the lists can exist independently
of a query.
In fact it makes a lot of sense; SQL conditions for a table might be reused across queries.
(Yes I know this is usually done via RDBMS views. Unfortunately, at least Oracle is extremely
poor at providing key and column metadata for views.)


Just providing data points :-)

Regards,
Jo

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