PHP 的 PDO 准备语句:我可以多次使用一个占位符吗

问题描述

我想执行以下查询:

选择*,(SELECT COUNT(*) FROM `tab2` WHERE `parent` = :id) AS `sum`从`tab1`哪里`id` = :id

如您所见，:id 占位符在查询中出现了两次.因此，如果我尝试使用以下命令执行此语句:

$q->execute(['id'=>$row_id]);

我收到错误:

致命错误:未捕获的异常PDOException"，消息为SQLSTATE[HY093]:参数编号无效

所以我必须重写准备好的查询并使用 :id1 和 :id2 占位符执行数组，这对我来说看起来有点愚蠢.

这是在准备好的语句的多个地方使用一个占位符的唯一方法吗?

PDO::prepare 表示

[y]你不能在准备好的语句中多次使用同名的命名参数标记，除非模拟模式打开.

由于通常最好关闭仿真模式(因此数据库执行准备好的语句)，因此您必须使用 id_0、id_1 等>

I'd like to perform the following query:

    SELECT
      *,
      (SELECT COUNT(*) FROM `tab2` WHERE `parent` = :id) AS `sum`
    FROM `tab1`
    WHERE `id` = :id

As you can see :id placeholder appeared twice in the query. So if I'd try to execute this statement with:

$q->execute(['id'=>$row_id]);

I'm receiving the error:

Fatal error:  Uncaught exception 'PDOException' with message 'SQLSTATE[HY093]: Invalid parameter number

So I have to rewrite the prepared query and execute array with :id1 and :id2 placeholders which looks a bit stupid for me.

Is it the only way to use one placeholder in several places of the prepared statement?

PDO::prepare states that

[y]ou cannot use a named parameter marker of the same name more than once in a prepared statement, unless emulation mode is on.

Since it's generally better to leave emulation mode off (so the database does the prepared statement), you'll have to use id_0, id_1, etc.

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