The following code is an example of an overly simple data retrieval function.
It is vulnerable to SQL injection because user-controlled data is inserted
directly into a query string: The application assumes that incoming data
always has a specific range of characters and ignores that some characters may
change the query logic to a malicious one.

In this particular case, the query can be exploited with the following string: 

----
' OR '1'='1
----

Using the UNION clause, an attacker would also be able to perform queries against
other tables and combine the returned data within the same query result.
