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