DATE: The DATE data type stores date and time information. Depending on your setup, the default display format for a date may be DD-MON-YY. For example, July 4, 2009, displays as 04-JUL-09. There are a number of functions you can use to change the display format or to show the time. You also have menu options in SQL Developer for customizing the display
NUMBER: Columns with the data type NUMBER allow only numeric data; no text, hyphens, or dashes are permitted. A column defined as NUMBER(5,2) can have a maximum of three digits before the decimal point and two digits after the decimal point. The first digit (5) is called the precision; the second digit (2) is referred to as the scale. The smallest allowed number is – 999.99, and the largest is 999.99. A column definition with a zero scale, such as NUMBER(5) or NUMBER(5,0), allows integers in the range from – 99,999 to 99,999.
VARCHAR2 AND CHAR: The VARCHAR2 and CHAR data types store alphanumeric data (for example, text, numbers, special characters). VARCHAR2 is the variable-length data type and the most commonly used alphanumeric data type; its maximum size is 4,000 characters. The main difference between VARCHAR2 and CHAR is that the CHAR data type is a fixed-length data type, and any unused room is blank padded with spaces
For example, a column defined as CHAR(10) and containing the four-character-length value JOHN in a row will have six blank characters padded at the end to make the total length 10 spaces. (If the column is stored in a VARCHAR2(10) column instead, it stores four characters only.) A CHAR column can store up to 2,000 characters.
If you want to store data containing more than 4,000 characters, you need to consider the CLOB data type, which allows you to store large amounts of textual data. It replaces the formerly used LONG data type, which is supported only for backward compatibility.
OTHER DATA TYPES: The data types BLOB and BFILE are binary data types that deal with access to multimedia content such as movies, images, or music. The main difference between these two data types is how the data is stored within the Oracle database. The BLOB data type stores the content inside the Oracle database, whereas the BFILE data type stores only a reference to the file location directory and the file name.