Are square brackets valid in an SQL query?

Question

I am looking at a note that someone wrote to me and it looks something like this:

SELECT Something FROM Foobar WHERE blah='blah'  --- [pulls this too - SELECT Something FROM Foobar WHERE something='elsehappens']

I'm trying to figure out if the --- [ comment - QUERY] is just a comment or if it actually means something I haven't seen before.

Answer 1

In this case it is just a comment... square brackets are often used to delimit real names for reserved words, or simply to delimit actual identifiers, but anything after a -- is always a comment.

Answer 2

They are generally used to indicate optional words or clauses. In this example, it appears to be nothing more than a comment as indicated in the manual: MySQL Comment Syntax

Answer 3

In MySQL, a -- comment is just a comment.

C-style comments with special characters may be used to give hints to the query optimizer, run version-specific queries etc:

CREATE TABLE mytable (id INT) /*!50000 ENGINE=InnoDB */ ;

This will create the table as InnoDB in MySQL 5.0 or higher, or with default engine in MySQL below 5.0.