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<?php |
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namespace Helix\DB\SQL; |
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use Helix\DB; |
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/** |
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* Represents a `CASE` expression, with or without a *subject* expression. |
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* |
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* If a subject is used, `WHEN` relies on equating the subject's evaluation to a literal value. |
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* This is also known as a "simple case", and is not null-safe. |
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* If you are choosing between known states, this may be the use-case for you. |
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* |
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* Otherwise `WHEN` relies on arbitrary predication. |
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* This is also known as a "searched case", and may be constructed in a null-safe manner. |
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* If you are choosing amongst complex states, this may be the use-case for you. |
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* |
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* With a subject (simple case): |
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* |
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* ``` |
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* CASE subject |
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* WHEN value THEN value |
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* ... |
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* END |
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* ``` |
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* |
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* Without a subject (searched case): |
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* |
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* ``` |
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* CASE |
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* WHEN predicate THEN value |
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* ... |
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* END |
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* ``` |
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*/ |
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class Choice extends Value { |
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/** |
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* @var string |
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*/ |
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protected $else; |
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/** |
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* @var string |
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*/ |
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protected $subject; |
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/** |
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* [when => then] |
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* |
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* @var string[] |
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*/ |
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protected $values = []; |
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/** |
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* @param DB $db |
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* @param string $subject |
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* @param array $values `[when => then]` for the subject. |
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*/ |
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public function __construct (DB $db, string $subject = null, array $values = []) { |
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parent::__construct($db, ''); |
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$this->subject = $subject; |
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$this->whenValues($values); |
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} |
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/** |
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* @return string |
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*/ |
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public function __toString () { |
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$sql = 'CASE'; |
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if (isset($this->subject)) { |
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$sql .= " {$this->subject}"; |
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} |
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foreach ($this->values as $when => $then) { |
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$sql .= " WHEN {$when} THEN {$then}"; |
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} |
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if (isset($this->else)) { |
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$sql .= " ELSE {$this->else}"; |
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} |
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$sql .= ' END'; |
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return $sql; |
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} |
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/** |
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* @param string|ValueInterface $else |
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* @return $this |
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*/ |
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public function else ($else) { |
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$this->else = isset($else) ? $this->db->quote($else) : null; |
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return $this; |
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} |
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/** |
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* Quotes and sets a conditional value. |
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* |
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* @param string|ValueInterface $expression |
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* @param string|ValueInterface $then |
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* @return $this |
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*/ |
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public function when ($expression, $then) { |
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$this->values[$this->db->quote($expression)] = $this->db->quote($then); |
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return $this; |
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} |
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/** |
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* Quotes and sets multiple conditional values for the subject. |
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* |
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* > :warning: Keys are quoted as literal values. |
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* > Use {@link when()} if you need an expression for the `WHEN` clause. |
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* |
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* @param array $values `[when => then]` |
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* @return $this |
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*/ |
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public function whenValues (array $values) { |
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foreach ($values as $when => $then) { |
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$this->when($when, $then); |
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} |
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return $this; |
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} |
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} |
hfw /
db
