Question

Mysql版本5.1。代码示例：

mysql_query("SELECT * FROM abonents WHERE `session_id`='$current_sess_id' UNION SELECT * FROM abonents_problem WHERE `session_id`='$current_sess_id' UNION SELECT * FROM abonents_stop WHERE `session_id`='$current_sess_id'");

如果删除“UNION”则运行，例如：

mysql_query("SELECT * FROM abonents WHERE `session_id`='$current_sess_id'" );

“WTF代码”永远=）：

$rez_11_one = mysql_query(
        "SELECT * FROM abonents WHERE `session_id`='$current_sess_id'"
    );
    $rez_11_two = mysql_query(
        "SELECT * FROM abonents_problem WHERE `session_id`='$current_sess_id'"
    );
    $rez_11_three = mysql_query(
        "SELECT * FROM abonents_stop WHERE `session_id`='$current_sess_id'"
    );
    if ($rez_11_one) {
        $rez_11 = $rez_11_one;
    } elseif ($rez_11_two) {
        $rez_11 = $rez_11_two;
    } else {
        $rez_11 = $rez_11_three;
    }

感谢您的帮助

Answer 1

对mysql文档UNION的引用仅在所有查询返回相同数量的columns时才有效。

http://dev.mysql.com/doc/refman/4.1/en/union.html

因此，当您使用选择器星号*时，我认为这些表具有不同的列数。使用select例如

SELECT 1,2 FROM foo UNION SELECT 1,2 FROM bar

为每个查询提供相同数量的列。

Answer 2

尝试不使用＆＃34; *＆＃34; 喜欢这个

mysql_query("SELECT <table_column_name> FROM abonents WHERE `session_id`='$current_sess_id' UNION SELECT <table_column_name> FROM abonents_problem WHERE `session_id`='$current_sess_id' UNION SELECT <table_column_name> FROM abonents_stop WHERE `session_id`='$current_sess_id'");

Answer 3

您可能需要在字符串中添加转义字符才能生成它：

mysql_query("SELECT * FROM abonents WHERE \`session_id\`=\'$current_sess_id\' UNION SELECT * FROM abonents_problem WHERE \`session_id\`=\'$current_sess_id\' UNION SELECT * FROM abonents_stop WHERE \`session_id\`=\'$current_sess_id\'");

Answer 4

确保查询返回相同数量的列。根据UNION的文档。它仅在查询返回相同列数时才有效

mysql select union不起作用

4 个答案: