空的變量,如果我有4個變量,我要選擇不同的值形成數據的基礎上PHP和MySQL:我怎麼能忽略從選擇
<?php
$var1 = ""; //this variable can be blank
$var2 = ""; //this variable can be blank
$var3 = ""; //this variable can be blank
$var4 = ""; //this variable can be blank
$result = mysql_query("SELECT DISTINCT title,description FROM table WHERE **keywords ='$var1' OR author='$var2' OR date='$var3' OR forums='$var4'** ");
?>
注:部分或全部變量($ VAR1,$ VAR2, $ VAR3,$ VAR4)可以爲空
我想要什麼: 我要忽視空字段
可以說是$ VAR1(關鍵字)爲空將選擇所有空的Fileds,但我想如果$ var1爲空結果將如
$result = mysql_query("SELECT DISTINCT title,description FROM table WHERE author='$var2' OR date='$var3' OR forums='$var4' ");
如果$ VAR2是空的,結果會是怎樣
$result = mysql_query("SELECT DISTINCT title,description FROM table WHERE keywords ='$var1' OR date='$var3' OR forums='$var4' ");
如果$ VAR1和$ VAR2是空的,結果會是怎樣
$result = mysql_query("SELECT DISTINCT title,description FROM table WHERE date='$var3' OR forums='$var4' ");
等
看一看蓋爾肖的博客文章這一功能[catch-all queries](http://sqlinthewild.co.za/index.php/2009/03/19/catch-all-queries/)。 – 2011-03-04 22:48:33