I have encountered some websites that when I used -- to comment the rest of the query it didn't work, but when I tried --+ it worked.
In the MySQL official documentation there is no such thing as --+ and we only have -- and two other ways.
Why does this happen (in detail)? I want to know exactly why this works sometimes and -- doesn't, and why there is no --+ for comments in the MySQL man page?
From the documentation:
From a -- sequence to the end of the line. In MySQL, the -- (double-dash) comment style requires the second dash to be followed by at least one whitespace or control character (such as a space, tab, newline, and so on). This syntax differs slightly from standard SQL comment syntax, as discussed in Section 1.8.2.4, “'--' as the Start of a Comment”.
(emphasis mine)
Many URL decoders treat + as a space.
MySQL requires a blank space followed by the double dashes like "-- " and a URL can't contain blank spaces but the + sign can be used as blank space. That's why these comments are followed up by "+".
