使用PDO获取单行、单列

你确定它会返回任何行吗?

$stmt->fetchColumn()

是获取单个值的正确方法,因此您可能没有绑定:user参数,或者它没有返回任何行。

$sql='SELECT some_col_name FROM table_name WHERE user=?';

$sth=$pdo_dbh->prepare($sql);
$data=array($user);

$sth->execute($data);

$result=$sth->fetchColumn();

我不知道为什么这么多人把事情搞砸了:

$stmt = $dbh->prepare("SELECT `column` FROM `table` WHERE `where`=:where"); 
$stmt->bindValue(':where', $MyWhere);
$stmt->execute();
$SingleVar = $stmt->fetchColumn();

确保您选择的是特定的 column * 或者,您需要在中指定列顺序号 fetchColumn() ,例如: $stmt->fetchColumn(2);

这只会在以下情况下正常工作: unique 'wheres' ; fetchColumn()

要获取最后一次插入,请将DESC Limit 1添加到sql语句中。

$sql = "SELECT `some_col_name` FROM table_name\n"

    . "ORDER BY `some_col_name` DESC\n"

    . "LIMIT 1";

$stmt = $conn->prepare($sql);
$result = $stmt->execute();
$row = $stmt->fetch(PDO::FETCH_ASSOC);
//convert the array content to string and store in variable 
$col = implode(" ", $row);
echo $col;

你先准备好声明了吗(之前 $stmt->execute() )

$stmt = $db->prepare("SELECT some_col_name FROM table_name WHERE user=:user");

$stmt->fetch(PDO::FETCH_COLUMN, $number_of_column);