Question

我有下表

uId | groupId
==============
1     12
3     66

如何编写mySQL语句来检查用户是否存在于组中？

我的尝试：

SELECT FROM usertable(uId) WHERE usertable.uId = $uId

上述查询仅检查用户是否存在，但不检查用户是否属于特定组。

Answer 1

只需将该条件附加到where子句中，例如：

SELECT uId
FROM usertable
WHERE usertable.uId = 1
AND groupId = 12

Answer 2

只需将groupId参数添加到查询WHERE子句中。

$userId = x; // some user id
$groupId = y; // some group id

$con; // your mysqli instance

if (!$stmt = $con->prepare('SELECT 1 FROM usertable WHERE uId = ? AND groupId = ?')) {
    throw new Exception($con->error, $con->errno);
}

$stmt->bind_param('ii', $userId, $groupId);

if (!$stmt->execute()) {
    throw new Exception($stmt->error, $stmt->errno);
}
if ($stmt->fetch()) {
    // user exists and is in group
}

Answer 3

$query = mysql_query("Select from usertable(uId) where usertable.uId = $uId and groupId=$gid");

if(mysql_num_rows($query)!=0){
echo "user exists!";
}else
{
echo "user not exists!";
}

检查用户是否存在mysql php

3 个答案: