4.3. Database-level checks

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Hibernate offers the `@Check` annotation so that you can specify an arbitrary SQL CHECK constraint which can be defined as follows:

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<div class="title">Example 217. Database check entity mapping example</div>
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<pre class="prettyprint highlight">`@Entity(name = "Book")
@Check( constraints = "CASE WHEN isbn IS NOT NULL THEN LENGTH(isbn) = 13 ELSE true END")
public static class Book {

    @Id
    private Long id;

    private String title;

    @NaturalId
    private String isbn;

    private Double price;

    //Getters and setters omitted for brevity

}`</pre>
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Now, if you try to add a `Book` entity with an `isbn` attribute whose length is not 13 characters,
a `ConstraintViolationException` is going to be thrown.

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<div id="stag::schema-generation-database-checks-persist-example" class="exampleblock">
<div class="title">Example 218. Database check failure example</div>
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<pre class="prettyprint highlight">`Book book = new Book();
book.setId( 1L );
book.setPrice( 49.99d );
book.setTitle( "High-Performance Java Persistence" );
book.setIsbn( "11-11-2016" );

entityManager.persist( book );`</pre>
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<pre class="prettyprint highlight">`INSERT  INTO Book (isbn, price, title, id)
VALUES  ('11-11-2016', 49.99, 'High-Performance Java Persistence', 1)

-- WARN SqlExceptionHelper:129 - SQL Error: 0, SQLState: 23514
-- ERROR SqlExceptionHelper:131 - ERROR: new row for relation "book" violates check constraint "book_isbn_check"`</pre>
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<div class="sect2">