Comment inline...
2017-03-28 20:36 GMT+02:00 Rob Sargent <robjsarg...@gmail.com>:
> Thank you again, all of these work:
>
> Map<String, PersonRecord> fullMap = new HashMap<>();
> fullMap.putAll(ctx.select(PERSON.fields())
> .from(PERSON.join(ALIAS)
> .on(PERSON.ID.equal(ALIAS.PERSON_ID)))
> .where(ALIAS.AKA.in(nameSet))
> .fetchMap(PERSON.NAME, r -> r.into(PERSON)));
>
> fullMap.putAll(ctx.select(PERSON.fields())
> .from(PERSON.join(ALIAS)
> .on(PERSON.ID.equal(ALIAS.PERSON_ID)
> .and(ALIAS.AKA.in(nameSet))))
> .fetchMap(PERSON.NAME, r -> r.into(PERSON)));
>
> fullMap.putAll(ctx.select(PERSON.fields())
> .from(PERSON.join(ALIAS)
> .on(PERSON.ID.equal(ALIAS.PERSON_ID))
> .and(ALIAS.AKA.in(nameSet)))
> .fetchMap(PERSON.NAME, r -> r.into(PERSON)));
>
> Is any more proper than the other?
>
The first one is what I'd choose here, because the WHERE predicate is
semantically sligthly different from the ON predicate. Your ALIAS.AKA
predicate is not stricly part of the JOIN specification, so I wouldn't put
it there.
For inner join, this is mostly just a stylistic debate (at least in most
databases). For outer join, 1 would be a very different query from 2/3
(which is another reason why stylistically, you should put the predicates
at the semantically right place).
2 and 3 are exactly the same thing. 2 is creating a Condition inside of ON,
whereas 3 is using TableOnConditionStep convenience API (which internally
does the same thing as 2 but leads to a bit less confusing parentheses).
Note, you could also write this, and it would still be the same as 2 and 3,
just using convenience API:
fullMap.putAll(ctx.select(PERSON.fields())
.from(PERSON)
.join(ALIAS)
.on(PERSON.ID.equal(ALIAS.PERSON_ID))
.and(ALIAS.AKA.in <http://alias.aka.in/>(nameSet))
.fetchMap(PERSON.NAME <http://person.name/>, r ->
r.into(PERSON)));
> I had gotten side tracked thinking I needed to use a RecordMapper but
> could never set that up properly.
>
Well, your lambda *is* a RecordMapper :) Just much more convenient syntax
than an anonymous or "normal" class.
Hope this helps,
Lukas
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