根据匹配字段，使用来自另一个数据库的数据更新MySQL数据库表

Question

Using PHP5, I'm needing to access two different databases (on the same server) but with different login credentials. Then get data from one database and update the other database for a record matching a unique field value. Here's what I have so far...

$link2->query("UPDATE db2.table2 
    INNER JOIN db1.table1 
        ON db1.table1.email = db2.table3.email 
SET db2.table2.field2 = db1.table1.field1");

Where I am totally lost is how to handle the fact that both databases have different connections. Which connection to I query? How do I incorporate the connection of the other database?

Answer 1

To use a single query to hit two different databases, two things must be true:

1. Those databases must be on the same MySQL server.
2. The username you use must have appropriate access to both databases, and all tables involved.

If these two conditions don't hold you need to retrieve the information to your program with a connection to one database, and then update the tables in the other database with its connection. That can sometimes be hard.

I believe your best bet in this case is to persuade your database administrator to add privileges to the account you use to modify db2 so it also has access to read db1 . (Of course that won't help if they're not on the sane server.)