22 lines
998 B
Plaintext
22 lines
998 B
Plaintext
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Syntax:
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<code>
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FROM <component_reference> [[LEFT | INNER] JOIN <component_reference>] ...
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</code>
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The {{FROM}} clause indicates the component or components from which to retrieve records. If you name more than one component, you are performing a join. For each table specified, you can optionally specify an alias.
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* The default join type is {{LEFT JOIN}}. This join can be indicated by the use of either {{LEFT JOIN}} clause or simply '{{,}}', hence the following queries are equal:
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<code>
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SELECT u.*, p.* FROM User u LEFT JOIN u.Phonenumber
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SELECT u.*, p.* FROM User u, u.Phonenumber p
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</code>
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* {{INNER JOIN}} produces an intersection between two specified components (that is, each and every record in the first component is joined to each and every record in the second component). So basically {{INNER JOIN}} can be used when you want to efficiently fetch for example all users which have one or more phonenumbers.
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<code>
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SELECT u.*, p.* FROM User u INNER JOIN u.Phonenumber p
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</code>
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