Database: What is a Synthetic Key?

By -
Well, a synthetic key is really the surrogate key. Primarily, in MySQL which commonly use a "current database" (non-temporal), surrogate key are either primary keys or columns that emphasizes uniquness with its column values but with its functionality that is a system generated like an auto increment key or a procedural generated that is not derived from any application data from a database. Usually, the most significant meaning of a surrogate key is the primary key.  It is also possible that the surrogate key exists in addition to the database-generated UUID (for example, an HR number for each employee other than the UUID of each employee).

Surrogate key is in contract to Natural Key which a natural key is defined customarily by the programmer or by the input, let say, is defined by it's national id number of a person or any number that is inputted from person's data that is not relying on a system generated UUID or a natural key is a user generated data, not system generated.

Surrogate key may differ in meaning when talking about Temporal Database. Please check or read from Wikipedia, http://en.wikipedia.org/wiki/Surrogate_key#Surrogates_in_practice.



Site's that can help you also understand what it means can be referenced here,

http://siebel.ittoolbox.com/groups/technical-functional/siebel-analytics-l/what-is-the-difference-between-a-primary-key-and-a-surrogate-key-1307246

http://en.wikipedia.org/wiki/Surrogate_key

http://blog.mclaughlinsoftware.com/2009/05/16/surrogate-keys-uses/

http://stackoverflow.com/questions/7971575/natural-key-vs-surrogate-key-an-innodb-foreign-key

Comments

Post a Comment

Popular posts from this blog

Converting sectors into MB - Useful in understanding the sectors in iostat in Linux

By -
Supposed you have a sector with 512 Bytes equivalent, then the formula will be just below 1 sect. 1024 Bytes 1024 KB --------- x ---------- x --------- = 2048 sect./ MB 512 Bytes 1 KB 1 MB i.e. if a sector has a 512 Bytes, commonly in a hard disk, so which means that a 1024 Bytes == 2 sector of a KiloByte. So if 2 sector is equivalent to a KiloByte (1024 Bytes), if you do the math, 2 ** 1024 / 512.0 = 2048. This is useful only understanding the iostat process in Linux.
Read more

What is Disk Contention?

By -
Okay, so let me take a note about this meaning... Disk contention occurs when multiple processes try to access the same disk simultaneously. Most disks have limits on both the number of accesses (I/O operations each second) and the amount of data they can transfer each second (I/O data rate, or  throughput ). When these limits are reached, processes must wait to access the disk. It's a situation occurring when multiple processes try to access the same disk(s) and the requests outrun the response times of the drive(s). This happens because most disks are restricted in the amount of data they can transfer and the number of accesses (I/O operations) they can handle each second. Disk contention became a more prominent problem when CPU speeds dramatically increased over the past 15 years, putting even greater demands on disk-based data storage and causing the modern data centers’ most significant operational constraint.
Read more

Installing MySQL from source: Could NOT find Curses (missing: CURSES_LIBRARY CURSES_INCLUDE_PATH)

By -
Just find this a terrible problem with my CentOS having x86_64 architecture and cmake failed to find the right library for Curses. Anyway, this is how I got the error when trying to build MySQL from source , $ cmake . -- Running cmake version 2.6.4 -- MySQL 5.6.12 -- Packaging as: mysql-5.6.12-Linux-x86_64 -- HAVE_VISIBILITY_HIDDEN -- HAVE_VISIBILITY_HIDDEN -- HAVE_VISIBILITY_HIDDEN -- Could NOT find Curses  (missing:  CURSES_LIBRARY CURSES_INCLUDE_PATH) CMake Error at cmake/readline.cmake:85 (MESSAGE):   Curses library not found.  Please install appropriate package,       remove CMakeCache.txt and rerun cmake.On Debian/Ubuntu, package name is libncurses5-dev, on Redhat and derivates it is ncurses-devel. Call Stack (most recent call first):   cmake/readline.cmake:128 (FIND_CURSES)   cmake/readline.cmake:202 (MYSQL_USE_BUNDLED_EDITLINE)   CMakeLists.txt:332 (MYSQL_CHECK_EDITLINE) -- Configuring incomplete, errors occur...
Read more