mysql - What is second level SQL Injection

Question

What is all about the second level SQL Injection.. This is with reference to the question Use of parameters for mysql_query.. and a part of one of the answers had this term...

Answer 1

I'm not exactly sure but I thought it was 'defined' in the post: Use of parameters for mysql_query

Excerpt (see point 2):

magic_quotes_gpc automatically escapes things you receive in requests from clients... but it cannot detect so-called second-level injections:

1. You get a malicious query from a client and store its contents in the database. magic_quotes_gpc prevents SQL injection; the malicious string gets stored correctly.
2. Later on, you fetch this string from the database and include it in another query. Now the string didn't come out of a request, so magic_quotes_gpc doesn't escape the string. Voilà, SQL injection; your data is now probably gone.

Here's another I've googled (http://www.osix.net/modules/article/?id=624):

Beware that variables inside a stored procedure aren't always immune to SQL Injection either. If the stored procedure contains constructs that add a second level of parsing, such as EXEC on a string in MS SQL Server, you will have to handle metacharacters again. This time inside the stored procedure.