是否存在IF NOT EXISTS mySQL查询？

just doing an INSERT using mySQL which works fine...

只是使用mySQL进行INSERT工作正常...

 mysql_query("INSERT INTO FLIGHTS_AVAILABLE 
 (aircraftID, aircraftType, maxSeats) VALUES('$theaircraftID', '$addType', '$maxCapacity'      ) ") 
or die(mysql_error());  

 echo '<p>';
 echo "The following details were added into the database:";
 echo "<hr>";

  echo $theaircraftID . $addType . $maxCapacity;

This works fine, however I've looked online and whilst I have heard of a feature called IF NOT EXISTS, there are not very good explanations online about it's use.

这工作正常，但我看过网上，虽然我听说过一个名为IF NOT EXISTS的功能，但在网上对它的使用并没有很好的解释。

Is there anyway, I can run this query above, providing that if for example $theaircraftID = 10, and there is already a row in the database where the aircraftID = 10, then the query would not be run?

无论如何，我可以在上面运行这个查询，假设如果例如$ theaircraftID = 10，并且数据库中已经有一行，其中aircraftID = 10，那么查询将不会运行？

Thanks for any help you may be able to suggest,

感谢您提供的任何帮助，

Tom

汤姆

2 个解决方案

#1

Add a UNIQUE INDEX on 'FLIGHTS_AVAILABLE'.'aircraftID'. MySQL will block additional INSERTs with the same value. Additionally you can use ON DUPLICATE KEY EXISTS to run an UPDATE incase the INSERT give a DUPLICATE KEY constraint error.

在'FLIGHTS_AVAILABLE'上添加UNIQUE INDEX。'aircraftID'。 MySQL将阻止具有相同值的其他INSERT。此外，您可以使用ON DUPLICATE KEY EXISTS运行UPDATE，INSERT提供DUPLICATE KEY约束错误。

#2

You can try to create unique index by required columns and then use INSERT IGNORE and mysql_affected_rows.

您可以尝试按必需列创建唯一索引，然后使用INSERT IGNORE和mysql_affected_rows。