How Can I Join Tables Across Different Databases in MySQL?

Detailed explanation of MySQL cross-database table connection

MySQL supports connecting tables in different databases. This feature is useful when you need to combine data from multiple databases into a single query.

To connect tables in different databases, you need to use fully qualified table names. A fully qualified table name consists of the database name, a dot (.) separator, and the table name.

For example, to join the table1 table in database A with the table2 table in database B, you can use the following syntax:

<code class="language-sql">SELECT <...>
FROM A.table1 t1 JOIN B.table2 t2 ON t2.column2 = t1.column1;</code>

In this example, the A.table1 and B.table2 prefixes indicate that the table1 and table2 tables are located in the A and B databases respectively.

It should be noted that users must have corresponding permissions on these two databases to perform connection operations. If the user does not have the necessary permissions, the query will fail.

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