What is the best technique to save images in the mysql database.Should I save images as blob data or save it in directories.The images will be showed every time the user visits his or her profile. -Thanks in advance.
The best technique would be to save them in the file-system and save their paths in the database.
The database is meant for data, the file-system for files.
The technique I used in the past to make sure there are no duplicates was to hash the contents of the file and save it as the result, so I get something like:
42efb15825666918118ba72128195246dbae4976.jpg
The actual name is saved in the database. This was, the chance of having duplicates is negligible.
The best technique is what Truth said, in addition, to guarantee that your images will have a unique name, use the current timestamp to rename them in your directory.