30 lines
994 B
PHP
30 lines
994 B
PHP
Syntax:
|
|
|
|
|
|
<code>
|
|
FROM <component_reference> [[LEFT | INNER] JOIN <component_reference>] ...
|
|
</code>
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
* 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:
|
|
<code>
|
|
SELECT u.*, p.* FROM User u LEFT JOIN u.Phonenumber
|
|
|
|
SELECT u.*, p.* FROM User u, u.Phonenumber p
|
|
</code>
|
|
|
|
* //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.
|
|
<code>
|
|
SELECT u.*, p.* FROM User u INNER JOIN u.Phonenumber p
|
|
</code>
|
|
|
|
|