I want to create a table, with a column which datatype will be LONG BLOB, what will be it's size?????
create table tab1(name varchar(20), pic longblob(?????????));

plz give me the currect code...........

Why do you need to specify the size? Why must it be a longblob instead of just blob? If you have the answer to the questions then you know what size to set. This really depends on the data that you are going to store. Perhaps you need to read the documentation on the blob data type in MySQL.

I don't believe you need to specify a size with blobs.