SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other unbuffered queries are activ

SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other unbuffered queries are active. Consider using PDOStatement::fetchAll(). Alternatively, if your code is only ever going to run against mysql, you may enable query buffering by setting the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute.

在PHP的PDO（PHP Data Objects）扩展中，这个错误SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other unbuffered queries are active通常发生在使用非缓冲查询（unbuffered queries）时，你尝试执行另一个查询，而前一个查询的结果集还没有被完全读取。
非缓冲查询允许你开始处理结果集的第一行，而不需要等待整个查询结果集都返回。然而，这意味着你不能在结果集完全读取之前执行另一个查询，因为这会导致上述错误。