Why should we sometimes use --+ instead of — in SQL injection to comment the rest of the query?

The name of the pictureThe name of the pictureThe name of the pictureClash Royale CLAN TAG#URR8PPP











up vote
9
down vote

favorite












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:



https://dev.mysql.com/doc/refman/8.0/en/comments.html



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?






http sql-injection mysql







share|improve this question



















  • 1




    I suppose your question is more related to HTTP than to SQL...
    – Your Common Sense
    11 hours ago






  • 2




    @YourCommonSense i had no idea its related to HTTP and not SQL, so why this happens?
    – Richard Jones
    10 hours ago










  • You can also use # which doesn't need a space after
    – paj28
    10 hours ago














up vote
9
down vote

favorite












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:



https://dev.mysql.com/doc/refman/8.0/en/comments.html



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?






http sql-injection mysql







share|improve this question



















  • 1




    I suppose your question is more related to HTTP than to SQL...
    – Your Common Sense
    11 hours ago






  • 2




    @YourCommonSense i had no idea its related to HTTP and not SQL, so why this happens?
    – Richard Jones
    10 hours ago










  • You can also use # which doesn't need a space after
    – paj28
    10 hours ago












up vote
9
down vote

favorite









up vote
9
down vote

favorite











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:



https://dev.mysql.com/doc/refman/8.0/en/comments.html



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?






http sql-injection mysql







share|improve this question















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:



https://dev.mysql.com/doc/refman/8.0/en/comments.html



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?






http sql-injection mysql




http sql-injection mysql






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 10 mins ago









Boann

1795




1795










asked 11 hours ago









Richard Jones

543




543







  • 1




    I suppose your question is more related to HTTP than to SQL...
    – Your Common Sense
    11 hours ago






  • 2




    @YourCommonSense i had no idea its related to HTTP and not SQL, so why this happens?
    – Richard Jones
    10 hours ago










  • You can also use # which doesn't need a space after
    – paj28
    10 hours ago












  • 1




    I suppose your question is more related to HTTP than to SQL...
    – Your Common Sense
    11 hours ago






  • 2




    @YourCommonSense i had no idea its related to HTTP and not SQL, so why this happens?
    – Richard Jones
    10 hours ago










  • You can also use # which doesn't need a space after
    – paj28
    10 hours ago







1




1




I suppose your question is more related to HTTP than to SQL...
– Your Common Sense
11 hours ago




I suppose your question is more related to HTTP than to SQL...
– Your Common Sense
11 hours ago




2




2




@YourCommonSense i had no idea its related to HTTP and not SQL, so why this happens?
– Richard Jones
10 hours ago




@YourCommonSense i had no idea its related to HTTP and not SQL, so why this happens?
– Richard Jones
10 hours ago












You can also use # which doesn't need a space after
– paj28
10 hours ago




You can also use # which doesn't need a space after
– paj28
10 hours ago










1 Answer
1






active

oldest

votes

















up vote
23
down vote













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.






share|improve this answer




















    Your Answer







    StackExchange.ready(function()
    var channelOptions =
    tags: "".split(" "),
    id: "162"
    ;
    initTagRenderer("".split(" "), "".split(" "), channelOptions);

    StackExchange.using("externalEditor", function()
    // Have to fire editor after snippets, if snippets enabled
    if (StackExchange.settings.snippets.snippetsEnabled)
    StackExchange.using("snippets", function()
    createEditor();
    );

    else
    createEditor();

    );

    function createEditor()
    StackExchange.prepareEditor(
    heartbeatType: 'answer',
    convertImagesToLinks: false,
    noModals: false,
    showLowRepImageUploadWarning: true,
    reputationToPostImages: null,
    bindNavPrevention: true,
    postfix: "",
    noCode: true, onDemand: true,
    discardSelector: ".discard-answer"
    ,immediatelyShowMarkdownHelp:true
    );



    );













     

    draft saved


    draft discarded


















    StackExchange.ready(
    function ()
    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fsecurity.stackexchange.com%2fquestions%2f196169%2fwhy-should-we-sometimes-use-instead-of-in-sql-injection-to-comment-the-re%23new-answer', 'question_page');

    );

    Post as a guest

















    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    23
    down vote













    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.






    share|improve this answer
























      up vote
      23
      down vote













      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.






      share|improve this answer






















        up vote
        23
        down vote










        up vote
        23
        down vote









        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.






        share|improve this answer












        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.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered 10 hours ago









        AndrolGenhald

        7,69441427




        7,69441427



























             

            draft saved


            draft discarded















































             


            draft saved


            draft discarded














            StackExchange.ready(
            function ()
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fsecurity.stackexchange.com%2fquestions%2f196169%2fwhy-should-we-sometimes-use-instead-of-in-sql-injection-to-comment-the-re%23new-answer', 'question_page');

            );

            Post as a guest
































































            Comments

            Post a Comment

            Popular posts from this blog

            Long meetings (6-7 hours a day): Being “babysat” by supervisor

            Image
            Clash Royale CLAN TAG #URR8PPP .everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty margin-bottom:0; up vote 31 down vote favorite 4 I hold a PhD in mechanical engineering with a 7 year background in self-guided, self-paced research including 2 years as a graduate level course instructor and a subject matter expert for various engineering projects in a university setting in the United States. For the last 10-11 months, I am working in a research industry in France where my task is to debug C++ spaghetti code written over a period of several years by my current supervisor. It is a team of 2: just I and my supervisor. Diurnally, I am posed with a "bug of the day" to get out of this C++ code. My supervisor generally gives me about 15-30 minutes to solve it and then accosts me about whether or not the task is completed and then rinses and repeats this until the end of the day. Off-late, my supervisor has been holding 6-7 hour long "meetin
            Read more

            Is the Concept of Multiple Fantasy Races Scientifically Flawed? [closed]

            Image
            Clash Royale CLAN TAG #URR8PPP up vote 2 down vote favorite Many fantasy worlds have multiple humanoid species (elves, orcs, humans, etc) living in the same world, in addition to that, they often have the ability to interbreed. And I can't help but question their believability... fantasy-races reproduction interspecies-relations share | improve this question edited Aug 9 at 14:46 Michael Kjörling ♦ 21.1k 10 85 161 asked Aug 9 at 13:13 Chlodio 118 6 closed as unclear what you're asking by MichaelK, Gryphon, John, Vincent, Frostfyre Aug 9 at 15:25 Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question. 3 Stack Exchange exist to
            Read more

            Confectionery

            Image
            Prepared foods made with a lot of sugar or other cabohydrates "Sweetmeat" redirects here. For the racehorse, see Sweetmeat (horse). Not to be confused with Sweetbread. This Kransekake is a traditional Scandinavian baker's confection. Confectionery is the art of making confections , which are food items that are rich in sugar and carbohydrates. Exact definitions are difficult. [1] In general, though, confectionery is divided into two broad and somewhat overlapping categories, bakers' confections and sugar confections. [2] Bakers' confectionery, also called flour confections , includes principally sweet pastries, cakes, and similar baked goods. Sugar confectionery includes candies ( sweets in British English), candied nuts, chocolates, chewing gum, bubble gum, pastillage, and other confections that are made primarily of sugar. In some cases, chocolate confections (confections made of chocolate) are treated as a separate category, as are sugar-free versions of
            Read more