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create table Dep(
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id INT UNSIGNED AUTO_INCREMENT primary key,
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dep varchar(255) not null unique,
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dep_sjm varchar(255),
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p_dep INT UNSIGNED default NULL
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);
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ALTER TABLE Dep
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ADD FOREIGN KEY (p_dep)
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REFERENCES Dep (id)
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ON UPDATE CASCADE;
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insert into Dep(id,dep,dep_sjm) values (209604,"sales department","XSB");
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insert into Dep(id, dep, dep_sjm, p_dep) values (203634,"sales department 1","XSB",209604);
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update Dep set id=48615 where id=209604;
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output: ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`test`.`Dep`, CONSTRAINT `Dep_ibfk_1` FOREIGN KEY (`p_dep`) REFERENCES `Dep` (`id`) ON UPDATE CASCADE)
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