[英]Why setting the group_concat_max_len variable in a query results in an error in PHP's bind_param()?
I have the following query: 我有以下查询:
$query = <<<SQL
SELECT
year,
count(*) AS `counter`,
GROUP_CONCAT(team) AS `team_list`
FROM
team_list
WHERE year IS NOT NULL
SQL;
if (!empty($sql)) { //$sql is an array of SQL WHERE statements "a IN (a,b,c)"
$query .= ' AND ' . implode(' AND ', $sql);
}
$query .= 'GROUP BY year ORDER BY year';
/////////////////////////////
//EXECUTING THE QUERIES
/////////////////////////////
//Filter count to know how many 's' variable have to be bind to the prepared statement
$filterCount = count($teams) + count($countries) + count($years) + count($rankings); //These are my ajax elements that are also used in the $sql variable
//Data query
$queryYears = $connection->prepare($query);
$queryYears->bind_param(str_repeat('s', $filterCount), ...$teams, ...$countries, ...$years, ...$rankings);
$queryYears-> execute();
This all works very fine! 这一切都很好!
However, once I try to enter SET SESSION group_concat_max_len = 1000000;
但是,一旦我尝试输入
SET SESSION group_concat_max_len = 1000000;
at the beginning of my query statement I get the following error: 在我的查询语句的开头我得到以下错误:
Fatal error: Uncaught Error: Call to a member function bind_param() on boolean
I understand that something is now wrong with my query, but when copy-pasting it to my DBMS the query can be executed without a problem. 我知道我的查询现在出现了问题,但是当将其复制粘贴到我的DBMS时,查询可以毫无问题地执行。
What am I doing wrong here? 我在这做错了什么?
Your problem is that you are trying to execute two queries at once, and mysqli::prepare
doesn't support that, so it fails and returns false. 你的问题是你试图一次执行两个查询,而
mysqli::prepare
不支持,所以它失败并返回false。 Instead, run the variable set as a separate query first: 而是首先将变量集作为单独的查询运行:
$connection->query("SET SESSION group_concat_max_len = 1000000;") or die($connection->error);
$queryYears = $connection->prepare($query) or die($connection->error);
// etc.
Note that you should be checking the status of your calls, as I have done in the code above. 请注意,您应该检查您的通话状态,就像我在上面的代码中所做的那样。
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