49 lines
1.3 KiB
Plaintext
49 lines
1.3 KiB
Plaintext
DQL GROUP BY syntax:
|
|
|
|
<code>
|
|
GROUP BY groupby_item {, groupby_item}*
|
|
</code>
|
|
|
|
DQL HAVING syntax:
|
|
|
|
<code>
|
|
HAVING conditional_expression
|
|
</code>
|
|
|
|
* GROUP BY and HAVING clauses can be used for dealing with aggregate functions
|
|
* Following aggregate functions are available on DQL: COUNT, MAX, MIN, AVG, SUM
|
|
|
|
Selecting alphabetically first user by name.
|
|
|
|
<code type="sql">
|
|
SELECT MIN(u.name) FROM User u
|
|
</code>
|
|
|
|
Selecting the sum of all Account amounts.
|
|
|
|
<code type="sql">
|
|
SELECT SUM(a.amount) FROM Account a
|
|
</code>
|
|
|
|
* Using an aggregate function in a statement containing no GROUP BY clause, results in grouping on all rows. In the example above we fetch all users and the number of phonenumbers they have.
|
|
|
|
<code type="sql">
|
|
SELECT u.*, COUNT(p.id) FROM User u, u.Phonenumber p GROUP BY u.id
|
|
</code>
|
|
|
|
* The HAVING clause can be used for narrowing the results using aggregate values. In the following example we fetch all users which have atleast 2 phonenumbers
|
|
|
|
<code type="sql">
|
|
SELECT u.* FROM User u, u.Phonenumber p HAVING COUNT(p.id) >= 2
|
|
</code>
|
|
|
|
<code type="php">
|
|
// retrieve all users and the phonenumber count for each user
|
|
|
|
$users = $conn->query("SELECT u.*, COUNT(p.id) count FROM User u, u.Phonenumber p GROUP BY u.id");
|
|
|
|
foreach($users as $user) {
|
|
print $user->name . ' has ' . $user->Phonenumber[0]->count . ' phonenumbers';
|
|
}
|
|
</code>
|