databaseclass-diagram
Why Do I need user id attribute?
I am currently trying to design a social network type of website and this is the class diagram
that I have so far
at the moment I have userId and username in separate tables because I wanted to normalize these tables but now I am not sure why do I need the userId attribute? I have done research and a lot of similar projects have this attribute but I don't get why? if the username is already going to uniquely identify a particular user.
By the way I am aware I have a problem with the requests table because at the moment with the attributes given I cannot identify a primary key Thanks
Solution
Two big reasons I can think of:
- Optimization. SQL databases typically perform far better when using integer primary keys than varchar ones. Lookup-something-by-user is one of the most common operations in this environment, so this has real performance implications. Many DBAs don't like GUID/UUIDs as PKs for exactly this reason.
- Nothing dictates that a username must uniquely identify users. Case in point: Stack Exchange user handles don't have to be unique, and are freely editable.
- How to list all the removable devices with DBus and UDisks2?
- gobject/gnome/glib bindings for D using GIR?
- How do nested functions get compiled?
- The "this" pointer and message receiving in D
- 64-bit executables with DMD
- GtkD with D lang on Fedora
- Why Android used Java concept instead of D language or C or C++? But Chromium web browser is in C++, its very complicated match
- How to use MongoItemWriter to write a List<T>
- Why a function with protected modifier can be overridden and accessible every where?
- Convert Unicode const(uint)* to a dlang character type
- Compiling D with Code::Blocks
- DMD vs. GDC vs. LDC
- Rendering a font in raylib using freetype
- Digital Mars D compiler; acquiring ASM output
- D Programming: openssl rsa forward reference compiler error
- D compiler DMD doesn't link object files
- OPTLINK: Warning 23: No Stack
- Is there a limit in the amount of temporary generated symbols during a project build using dmd 2.063?
- Is this the right way to combine Garbage collected with none Garbage collected code in D
- D compiler (Digital Mars D Compiler) throwing error
- Which D Compiler to Use?
- Splitting a string treating multiple whitespace as one separator
- Proper way of passing array parameters to D functions
- Detailed Valgrind internals documentation
- Is it possible, in D, to tell the garbage collector to not scan a particular pointer (or anything below it)?
- Iterate over key/value pairs in associative array in D.
- Dlang associative array of an array of strings keyed by a string has unexpected behavior
- How to repeat a statement N times (simple loop)
- Is worth the effort to learn D?
- ld: undefined reference to object I can see in objdump