Implicit join type
Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
jOOQ's very useful implicit JOIN feature can be used to use a path notation to join tables on their actual, or synthetic foreign keys. For example:
// Get all books, their authors, and their respective language
create.select(
BOOK.author().FIRST_NAME,
BOOK.author().LAST_NAME,
BOOK.TITLE,
BOOK.language().CD.as("language"))
.from(BOOK)
.fetch();
By default, this produces:
- An
INNER_JOINif all columns of the foreign key areNOT NULL - A
LEFT_JOINif the foreign key is nullable / optional
The above defaults are important to prevent implicit joins from filtering results when placed in clauses that are not meant to filter, such as the SELECT clause or the ORDER BY clause.
Users may prefer to enforce a different behaviour, including:
- Always produce a
LEFT_JOIN, e.g. because this was the behaviour before jOOQ 3.14 - Always produce an
INNER_JOIN, e.g. because they're migrating off Hibernate / JPA, and depend on Hibernate's implicit joins producing inner joins
This change of behaviour can be achieved with the following setting:
Example configuration
Settings settings = new Settings()
.withRenderImplicitJoinType(RenderImplicitJoinType.INNER_JOIN);
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