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be01b7eec5
This adds the possibility to manage data on a normalized relational database in N:M relations. On the relation editor in a form, the tools to add, delete, link and unlink work (also) on the linking table if a relation is visualized as N:M relation. Configuration is done through the fields tab where on the relation a second relation can be chosen (if there is a suitable relation in terms of a second relation on the linking table). Limitations =========== QGIS is not a database management system. It is based on assumptions about the underlying database system. In particular it expects * A `ON DELETE CASCADE` or similar measure on the second relation * Does not take care of setting the primary key when adding features. Either users need to be instructed to set them manually or - if it's a database derived value - the layers need to be in transaction mode (currently only activatable through the API)
62 lines
1.6 KiB
SQL
62 lines
1.6 KiB
SQL
-- Table: qgis_test.authors
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-- DROP TABLE qgis_test.authors;
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CREATE TABLE qgis_test.authors
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(
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pk serial NOT NULL,
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name character varying(255),
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CONSTRAINT authors_pkey PRIMARY KEY (pk),
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CONSTRAINT authors_name_key UNIQUE (name)
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);
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-- Table: qgis_test.books
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-- DROP TABLE qgis_test.books;
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CREATE TABLE qgis_test.books
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(
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pk serial NOT NULL,
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name character varying(255),
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CONSTRAINT books_pkey PRIMARY KEY (pk),
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CONSTRAINT books_name_key UNIQUE (name)
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);
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-- Table: qgis_test.books_authors
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-- DROP TABLE qgis_test.books_authors;
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CREATE TABLE qgis_test.books_authors
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(
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fk_book integer NOT NULL,
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fk_author integer NOT NULL,
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CONSTRAINT books_authors_pkey PRIMARY KEY (fk_book, fk_author),
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CONSTRAINT books_authors_fk_author_fkey FOREIGN KEY (fk_author)
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REFERENCES qgis_test.authors (pk) MATCH SIMPLE
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ON UPDATE NO ACTION ON DELETE CASCADE,
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CONSTRAINT books_authors_fk_book_fkey FOREIGN KEY (fk_book)
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REFERENCES qgis_test.books (pk) MATCH SIMPLE
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ON UPDATE NO ACTION ON DELETE CASCADE
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);
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INSERT INTO qgis_test.authors(name)
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VALUES
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('Erich Gamma'),
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('Richard Helm'),
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('Ralph Johnson'),
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('John Vlissides'),
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('Douglas Adams'),
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('Ken Follett'),
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('Gabriel García Márquez');
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INSERT INTO qgis_test.books(name)
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VALUES
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('Design Patterns. Elements of Reusable Object-Oriented Software');
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INSERT INTO qgis_test.books_authors(fk_book, fk_author)
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VALUES
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(1, 1),
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(1, 2),
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(1, 3),
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(1, 4);
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