Datatypes

MSSQL

• Numeric:
  • bigint, int, smallint, decimal, money
• Approximate:
  • float, real (avoid these datatypes and use decimal instead??)
• Date/Time:
  • date, time, datetime
• Char string:
  • char, varchar (varchar defines max size while char defines exact size)
• Unicode Char String:
  • nchar, nvarchar (takes more space because of unicode)
• Binary String:
  • binary, varbinary
• Others:
  • geometry (euclidean flat coordinates - longitude/latitude)
  • geographic (round earth coordinate system)

varchar vs varchar2

• varchar2 only exists in oracle, not in sql server
• They are practically synonymous, and exists only due to historical reasons

GIS

• Geographic Information System
• It is a system to manage geographic data such as coordinates
• Organization: OpenGIS (http://www.opengeospatial.org/)
• Examples:
  • Postgresql (via PostGIS)
  • MySQL
  • MSSQL

Geometry vs Geographic type

• Geometry coordinates are represented by longitude and latitude
• Geometry is supported more
• Seems like Geometry datatype returns distance in degrees while geographic type returns in meters
• https://postgis.net/workshops/postgis-intro/geography.html

COLLATION

• assigning some order to the characters in an Alphabet, say, ASCII or Unicode etc.