由于某些原因,使用以下代码组合多个表不起作用。我想删除重复项,因此我假设 UNION 使用正确,不使用UNION ALL。
如何将database1,database2和database3中的所有三个数据库表组合到database4中的单个表中?
所有数据库表都具有相同的结构。
<?php
// Variable definitions omitted
// Connect to all 4 Databases
$connection1 = mysql_connect($host1, $username1, $password1) or die ('Cannot connect to the database because: ' . mysql_error());
$connection2 = mysql_connect($host2, $username2, $password2) or die ('Cannot connect to the database because: ' . mysql_error());
$connection3 = mysql_connect($host3, $username3, $password3) or die ('Cannot connect to the database because: ' . mysql_error());
$connection4 = mysql_connect($host4, $username4, $password4) or die ('Cannot connect to the database because: ' . mysql_error());
// Merge all 4 Databases into the Search Database 4
mysql_select_db ($database4);
mysql_query("
SELECT * FROM $database4.$TableName4
UNION
SELECT * FROM $database1.$TableName1
UNION
SELECT * FROM $database2.$TableName2
UNION
SELECT * FROM $database3.$TableName3
");
// Close databases connections
mysql_close($connection1);
mysql_close($connection2);
mysql_close($connection3);
mysql_close($connection4);
?>