Data Types

First, we need to cover the various data types available (see Table 3-1). Data types are like variable types. In some languages, you have strings, integers, floating-point numbers, big integers, characters, and so on. The same holds true for database data types: There are different data descriptors for different types of data. Every column in the database is for storing a particular kind of data: a column for storing last names would be of type 'varchar', a column for storing birthdates should be of type 'date', and so on. This helps the database store the information more efficiently and helps the programmer know what kind of data to expect.

Table 3-1: Common Data Types

Name	Type	Description	Notes
INT	Numeric	Signed four-byte integer	-2147483648 to [phone]
SMALLINT	Numeric	Signed two-byte integer	-32768 to +32767
REAL	Numeric	Variable precision	6 decimal digits precision
CHAR(n)	Character	Fixed-length char string	Holds n characters
VARCHAR(n)	Character	Variable-length char string	Holds up to n characters
BLOB	Binary	Binary Large OBject	For storing large binary data
Name	Type	Description	Notes
DATE	Date	Date storage	Ex. YYYY-MM-DD
TIME	Time	Time storage	Ex. HH:MM:SS
TIMESTAMP	Date/Time	Date & Time storage	Ex. YYYY-MM-DD HH:MM:SS