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Catalog and schema expressions

Applies to ✅ Open Source Edition   ✅ Express Edition   ✅ Professional Edition   ✅ Enterprise Edition

Most databases know some sort of namespace to group objects like tables, stored procedures, sequences and others into a common catalog or schema. jOOQ uses the types org.jooq.Catalog and org.jooq.Schema to model these groupings, following SQL standard naming.

The catalog

A catalog is a collection of schemas. In many databases, the catalog corresponds to the database, or the database instance. Most often, catalogs are completely independent and their tables cannot be joined or combined in any way in a single query. The exception here is SQL Server and Sybase ASE, which allow for fully referencing tables from multiple catalogs:

SELECT *
FROM [Catalog1].[Schema1].[Table1] AS [t1]
JOIN [Catalog2].[Schema2].[Table2] AS [t2] ON [t1].[ID] = [t2].[ID]

Some dialects, including MariaDB, MemSQL, MySQL, use catalogs (databases) and schemas as the same thing. jOOQ treats databases in those dialects as schemas instead.

By default, the Settings.renderCatalog flag is turned on. In case a database supports querying multiple catalogs, jOOQ will generate fully qualified object names, including catalog name. For more information about this setting, see the manual's section about settings

jOOQ's code generator generates subpackages for each catalog.

The schema

A schema is a collection of objects, such as tables. Most databases support some sort of schema (except for some embedded databases like Access, Firebird, SQLite). In most databases, the schema is an independent structural entity. In Oracle, the schema and the user / owner is mostly treated as the same thing. An example of a query that uses fully qualified tables including schema names is:

SELECT *
FROM "Schema1"."Table1" AS "t1"
JOIN "Schema2"."Table2" AS "t2" ON "t1"."ID" = "t2"."ID"

By default, the Settings.renderSettings flag is turned on. jOOQ will thus generate fully qualified object names, including the setting name. For more information about this setting, see the manual's section about settings

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