由于我如何在表格中獲取信息，我需要建立一個聯合來顯示交叉引用。Tablebrand1 是表的名稱。2 和 3Tablebrand1CODE CROSSREFERENCEA15 SAMSUNG A10A16 SAMSUNG A20A63 SAMSUNG A30Tablebrand2CODE CROSSREFERENCEX63 SAMSUNG A10X64 SAMSUNG A20X65 SAMSUNG A30Tablebrand3CODE CROSSREFERENCETOP99 SAMSUNG A10TOP98 SAMSUNG A20TOP97 SAMSUNG A30SQL查詢(SELECT "Tablebrand1" AS `brand`, CROSSREFERENCE as `code` FROM Tablebrand1 WHERE CROSSREFERENCE = 'SAMSUNG A10')UNION (SELECT "Tablebrand2" AS `brand`, CROSSREFERENCE as `code` FROM Tablebrand2 WHERE CROSSREFERENCE = 'SAMSUNG A10')UNION(SELECT "Tablebrand3" AS `brand`, CROSSREFERENCE as `code` FROM Tablebrand3 WHERE CROSSREFERENCE = 'SAMSUNG A10');查詢正確地顯示了它，但是當嘗試在 php 中顯示它時，我收到一個來自查詢的錯誤，因為如果我修改它以進行更簡單的查詢，它會正確地顯示數據。<?phpecho "<table style='border: solid 1px black;'>";echo "<tr><th>brand</th><th>code</th></tr>";class TableRows extends RecursiveIteratorIterator { function __construct($it) { parent::__construct($it, self::LEAVES_ONLY); } function current() { return "<td style='width:150px;border:1px solid black;'>" . parent::current(). "</td>"; } function beginChildren() { echo "<tr>"; } function endChildren() { echo "</tr>" . "\n"; }}$servername = "localhost";$username = "user";$password = "pass";$dbname = "dbname";try { $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password); $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); $stmt = $conn->prepare("((SELECT "Tablebrand1" AS `brand`, CROSSREFERENCE as `code` FROM Tablebrand1 WHERE CROSSREFERENCE = 'SAMSUNG A10')UNION (SELECT "Tablebrand2" AS `brand`, CROSSREFERENCE as `code` FROM Tablebrand2 WHERE CROSSREFERENCE = 'SAMSUNG A10')UNION我的代碼如下，我對 php 和 union 的了解很少。
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您沒有說明錯誤消息是什么，但一個明顯的錯誤是您使用的引號沒有被轉義。(另外，在查詢開始時您有太多的引號( "((SELECT...) 因此您需要像這樣轉義查詢中的引號
$stmt = $conn->prepare("
(SELECT \"Tablebrand1\" AS `brand`, CROSSREFERENCE as `code`
FROM Tablebrand1 WHERE CROSSREFERENCE = 'SAMSUNG A10')
UNION
(SELECT \"Tablebrand2\" AS `brand`, CROSSREFERENCE as `code`
FROM Tablebrand2 WHERE CROSSREFERENCE = 'SAMSUNG A10')
UNION
(SELECT \"Tablebrand3\" AS `brand`, CROSSREFERENCE as `code`
FROM Tablebrand3 WHERE CROSSREFERENCE = 'SAMSUNG A10');"
);
或者，您可以在查詢中使用單引號，而不是像這樣的雙引號
$stmt = $conn->prepare("
(SELECT 'Tablebrand1' AS `brand`, CROSSREFERENCE as `code`
FROM Tablebrand1 WHERE CROSSREFERENCE = 'SAMSUNG A10')
UNION
(SELECT 'Tablebrand2' AS `brand`, CROSSREFERENCE as `code`
FROM Tablebrand2 WHERE CROSSREFERENCE = 'SAMSUNG A10')
UNION
(SELECT 'Tablebrand3' AS `brand`, CROSSREFERENCE as `code`
FROM Tablebrand3 WHERE CROSSREFERENCE = 'SAMSUNG A10');"
);
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