Hi, Kenneth, On Fri, 2002-03-08 at 08:48, Kenneth Hylton wrote: > I've posted this twice before - third time might be the charmer... > Can anybody help me? > I am using the C API and am returning a result set from a table with a BLOB > type item in it. > When I populate the BLOB fields initially (with all the same data) the > length is returned properly when I issue SELECT * FROM <table> and decode > the result set column metadata. > Meaning, that if I put , "This Blob's for you!" in the column, the value of > MYSQL_FIELDS.length = 65535 (max of BLOB type) and MYSQL_FIELDS.max_length = > 21. > When I update a few rows and put, "That's OK man, but you still can't have > my BLOB!" in a few columns, the values for the length of the fields are > returned funny, or at least, I don't understand why they are returning they > way they are. > Meaning the value of the new column length are all set to > MYSQL_FIELDS.length = 65535 (again, max of BLOB type) and > MYSQL_FIELDS.max_length = 49. Problem is, this is even on the unchaged > rows! Yuk! > A little experimentation showed that if I select on only unchanged rows, the > length is returned as 21. But, if the result set has one of the changed > rows in it, the length of all blob fields is returned as 49, when (at least > to me) it should be 21 or 49. > In other words, it returns as the BLOB max_length value the value of the > longest blob in the result set, NOT the max_length of each row. I inserted > (and updated) some records in the table with BLOB contents "It's all about > the BLOB" and I see the same result. It returns not the length of the BLOB > for the row, but the length of the longest BLOB field in the result set.
This is correct behaviour. If you wanted to print out the result in a table layout, you'll want to know the max length of each column in the result set. That's why the field is called MYSQL_FIELDS.max_length. > We are running MySQL 3.23.46-Max on RedHat 7.2 Question: > 1) How do I get the actual length of the BLOB column in the row, > without storing a separate column to maintain BLOB length manually? mysql_field_lengths(), which you can call after mysql_fetch_row(), and naturally the result will be unique for each row. > 2) If this is not a problem because there is some other way to tell > where the BLOB buffer ends, please let me know. See #1. Regards, Arjen. -- MySQL Training in Brisbane: 18-22 March, http://www.mysql.com/training/ __ ___ ___ ____ __ / |/ /_ __/ __/ __ \/ / Mr. Arjen G. Lentz <[EMAIL PROTECTED]> / /|_/ / // /\ \/ /_/ / /__ MySQL AB, Technical Writer, Trainer /_/ /_/\_, /___/\___\_\___/ Brisbane, QLD Australia <___/ www.mysql.com --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
