MySql php：检查行是否存在
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MySql php: check if Row exists
提问by Jeff
This is probably an easy thing to do but I'm an amateur and things just aren't working for me.
这可能是一件容易做的事情，但我是一个业余爱好者，事情对我不起作用。
I just want to check and see if a row exists where the $lectureName shows. If a row does exist with the $lectureName somewhere in it, I want the function to return "assigned" if not then it should return "available". Here's what I have. I'm fairly sure its a mess. Please help.
我只想检查 $lectureName 显示的位置是否存在一行。如果某行确实存在带有 $lectureName 的行，我希望该函数返回“已分配”，如果没有，则它应该返回“可用”。这就是我所拥有的。我很确定它是一团糟。请帮忙。
function checkLectureStatus($lectureName)
{
$con = connectvar();
mysql_select_db("mydatabase", $con);
$result = mysql_query("SELECT * FROM preditors_assigned WHERE lecture_name='$lectureName'");
while($row = mysql_fetch_array($result));
{
if (!$row[$lectureName] == $lectureName)
{
mysql_close($con);
return "Available";
}
else
{
mysql_close($con);
return "Assigned";
}
}
When I do this everything return available, even when it should return assigned.
当我这样做时，一切都返回可用，即使它应该返回分配。
回答by kijin
Easiest way to check if a row exists:
检查行是否存在的最简单方法：
$lectureName = mysql_real_escape_string($lectureName); // SECURITY!
$result = mysql_query("SELECT 1 FROM preditors_assigned WHERE lecture_name='$lectureName' LIMIT 1");
if (mysql_fetch_row($result)) {
return 'Assigned';
} else {
return 'Available';
}
No need to mess with arrays and field names.
无需弄乱数组和字段名称。
回答by quickshiftin
This ought to do the trick: just limit the result to 1 row; if a row comes back the $lectureNameis Assigned, otherwise it's Available.
这应该可以解决问题：只需将结果限制为 1 行；如果一行返回$lectureNameis Assigned，否则它是Available。
function checkLectureStatus($lectureName)
{
$con = connectvar();
mysql_select_db("mydatabase", $con);
$result = mysql_query(
"SELECT * FROM preditors_assigned WHERE lecture_name='$lectureName' LIMIT 1");
if(mysql_fetch_array($result) !== false)
return 'Assigned';
return 'Available';
}
回答by Starx
Use mysql_num_rows(), to check if rows are available or not
使用 mysql_num_rows()，检查行是否可用
$result = mysql_query("SELECT * FROM preditors_assigned WHERE lecture_name='$lectureName' LIMIT 1");
$num_rows = mysql_num_rows($result);
if ($num_rows > 0) {
// do something
}
else {
// do something else
}
回答by juergen d
$result = mysql_query("select if(exists (SELECT * FROM preditors_assigned WHERE lecture_name='$lectureName'),'Assigned', 'Available')");
回答by Hardeep Pandya
If you just want to compare only one row with $lactureName then use following
如果您只想将一行与 $lactureName 进行比较，请使用以下内容
function checkLectureStatus($lectureName)
{
$con = connectvar();
mysql_select_db("mydatabase", $con);
$result = mysql_query("SELECT * FROM preditors_assigned WHERE lecture_name='$lectureName'");
if(mysql_num_rows($result) > 0)
{
mysql_close($con);
return "Assigned";
}
else
{
mysql_close($con);
return "Available";
}
}
回答by Your Common Sense
function checkLectureStatus($lectureName) {
global $con;
$lectureName = mysql_real_escape_string($lectureName);
$sql = "SELECT 1 FROM preditors_assigned WHERE lecture_name='$lectureName'";
$result = mysql_query($sql) or trigger_error(mysql_error()." ".$sql);
if (mysql_fetch_row($result)) {
return 'Assigned';
}
return 'Available';
}
however you have to use some abstraction library for the database access.
the code would become
但是你必须使用一些抽象库来访问数据库。
代码将成为
function checkLectureStatus($lectureName) {
$res = db::getOne("SELECT 1 FROM preditors_assigned WHERE lecture_name=?",$lectureName);
if($res) {
return 'Assigned';
}
return 'Available';
}
