php 使用 PDO 获取单行单列
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/1666710/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Fetching single row, single column with PDO
提问by Chris
I have a mysql query that targets a single column in a single row
我有一个针对单行中的单列的 mysql 查询
"SELECT some_col_name FROM table_name WHERE user=:user"
After I execute the statement $stmt->execute();how do I get this single cell directly placed into a variable with no loops? In other words how to get
执行语句后，$stmt->execute();如何将这个单个单元格直接放入没有循环的变量中？换句话说，如何获得
from $stmt->execute();
to $col_value = 100;
I tried the 2 below, but neither worked.. The column is number 4 in the original table, but I'm assuming since in my select statement I'm selecting it only, it should be 1 when I specify the parameter for fetchColumn.
我尝试了下面的 2，但都没有工作.. 该列在原始表中是 4，但我假设因为在我的 select 语句中我只选择它，当我为 fetchColumn 指定参数时它应该是 1。
$col_value = $stmt->fetchColumn();
$col_value = $stmt->fetchColumn(0);
As you can see, I'm trying to do it in as few lines as possible.
正如你所看到的，我试图用尽可能少的行来完成。
回答by reko_t
Are you sure it's returning any rows? $stmt->fetchColumn()
is correct way to fetch a single value, so either you probably didn't bind the :user parameter or it simply returned no rows.
你确定它返回任何行吗？$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，或者它只是不返回任何行。
回答by JAL
$sql='SELECT some_col_name FROM table_name WHERE user=?';
$sth=$pdo_dbh->prepare($sql);
$data=array($user);
$sth->execute($data);
$result=$sth->fetchColumn();
回答by Matthew
I'm not sure why so many people mess this up:
我不知道为什么这么多人搞砸了：
$stmt = $dbh->prepare("SELECT `column` FROM `table` WHERE `where`=:where");
$stmt->bindValue(':where', $MyWhere);
$stmt->execute();
$SingleVar = $stmt->fetchColumn();
Make sure that you are selecting a specific columnin the query and not *or you will need to specify the column order number in fetchColumn(), example: $stmt->fetchColumn(2);That usually isn't a good idea because the columns in the database may be reorganized by, someone...
确保您column在查询中选择了特定的而不是，*否则您将需要在 中指定列顺序号fetchColumn()，例如：$stmt->fetchColumn(2);这通常不是一个好主意，因为数据库中的列可能被某人重新组织...
This will only work properly with unique 'wheres'; fetchColumn()will not return an array.
这只适用于unique 'wheres'; fetchColumn()不会返回数组。
回答by Cold Pen
When you want to get the last insert you add the DESC Limit 1 to the sql statement.
当您想要获得最后一个插入时，您可以将 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;
回答by 1nstinct
You could use this:
你可以用这个：
$stmt->fetch(PDO::FETCH_COLUMN, $number_of_column);
回答by True Soft
Have you prepared the statement first? (Before $stmt->execute())
你先准备好声明了吗？（之前$stmt->execute()）
$stmt = $db->prepare("SELECT some_col_name FROM table_name WHERE user=:user");
