30 lines
1001 B
PHP
30 lines
1001 B
PHP
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.
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If you name more than one component, you are performing a join.
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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).
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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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