如何使用PHP获取MySQL表中的行数？

Question

为什么我的代码在$result = mysql_query("SELECT * FROM institutions");行上返回500 Internal Server错误$result = mysql_query("SELECT * FROM institutions"); 我做错什么了吗？ 我想要做的就是在我刚向该表添加一行后计算MySQL表（称为“机构”）中的行数。

    $institution_sql = "
    INSERT INTO `institutions`
    (`InstitutionName`, `HeaderPictureID`, `Description`, `DevicesInfo`, `DoingInfo`, `FacebookPage`, `Location`, `TwitterHandle`, `Website`, `CreatedAt`)
    VALUES
    (" . nz($_POST['TempInstitutionName']) . ", 74, 'N/A', 'N/A', 'N/A', 'N/A', 'On the Internet', 'N/A', 'N/A', NOW())
    ";

    $mysqli->query($institution_sql);
    if ($mysqli->errno) {
        $dbreturn['status'] = "PASSWORD_FAILURE";
    } else {
        $dbreturn['status'] = "EXEC_SUCCESS";

        $result = mysql_query("SELECT * FROM institutions");
        $rows = mysql_num_rows($result);
        echo "There are " . $rows . " rows in my table.";

        $insert_sql = "
        INSERT INTO `users`
        (`Handle`, `Email`, `FirstName`, `LastName`, `InstitutionID`, `TempInstitutionName`, `TwitterHandle`, `ProfilePictureID`, `HeaderPictureID`, `AccountType`, `CreatedAt`)
        VALUES
        (" . nz($_POST['Handle']) . ", " . nz($_POST['Email']) . ", " . nz($_POST['FirstName']) . ", " . nz($_POST['LastName']) . ", $num_rows, " . nz($_POST['TempInstitutionName']) . ", " . nz($_POST['TwitterHandle']) . ", " . nz('75') . ", " . nz('74') . ", " . nz($_POST['AccountType']) . ",NOW())
        ";

        $mysqli->query($insert_sql);
        if ($mysqli->errno) {
            $dbreturn['status'] = "EXEC_FAILURE";
        } else {
        $dbreturn['status'] = "EXEC_SUCCESS";

        $insertid = $mysqli->insert_id;

        $password_sql = "
        INSERT INTO `passwords`
        (`UserID`)
        VALUES
        ('$insertid')
        ";

        $mysqli->query($password_sql);
        if ($mysqli->errno) {
            $dbreturn['status'] = "PASSWORD_FAILURE";
        } else {
            $dbreturn['status'] = "EXEC_SUCCESS";
        }

        } //todo: use a transaction here

    }

Answer 1

$ result = mysql_query（“ SELECT count（*）FROM机构”）;

这将直接返回行数。

该链接可以为您提供详细信息

http://dev.mysql.com/doc/refman/5.1/zh-CN/counting-rows.html

Answer 2

您的问题是您将MYSQLI与MYSQL混合使用

使用mysqli重写代码

    $result = $mysqli->query("SELECT * FROM institutions");
    $rows = $result->num_rows ;
  //  and so on ...

您通过mysqli连接，然后在代码中使用mysql。

Answer 3

采用

$result = $mysqli->query($institution_sql);
$result->num_rows;

或用于普通的旧mysql

$result = mysql_query($institution_sql);
mysql_num_rows($result);

Answer 4

尝试这个：

$result = mysql_query("SELECT count(*) FROM institutions");

MySQL说明文件： http ： //dev.mysql.com/doc/refman/5.0/en/select.html

还要这样： http : //www.w3schools.com/sql/sql_func_count.asp

SQL COUNT(*) Syntax

COUNT（*）函数返回表中的记录数：

Answer 5

...也应该是：

VALUES（'“。nz（$ _ POST ['TempInstitutionName']）。”'，74

请注意单引号[除非'nz'函数可以解决]。