Saturday, June 09, 2007

ORACLE Datatypes Basics

-> Char contain alphanumeric data.
-> Length of Char datatype is between 1 and 255 characters.
-> If you don't specify a length, a char column stores a single character by default.
-> Char datatypes stores data in the Fixed-Length Format.
-> Be aware, when using this data type, that spaces are padded to the right of the value to supplement the total allocated length of the column.
-> It can be declared as char(size) where size is the total length allowed for a value in a column defined as char.

-> Date datatype is used to store all date and Time information.
-> Oracle always allocates a Fixed - 7 bytes for a DATE column.
-> Oracle uses the default format of DD-MON-YY for entering and displaying.
-> Following Include as a Part of DATE are century, year, month, day, hour, minute and second.
-> It enables you to store dates in range of January 1, 4712 B.C. To December 31, 4712 A.D.
-> To view System Date and time we can use the SQL function called SYSDATE.

-> It can store alphanumeric strings.
-> It stores the data in Variable-Length Format.
-> Length of Long rise upto 2 giga bytes.
-> Long is used to store more than 2000 characters in a column.
-> You cannot use any of Oracle's built-in functions or operator with LONG column.
-> You can think of a LONG column as a large container into which you can store or retrieve data but not manipulate it.
Limitations of LONG data type are as under
i> Only one column in a table can have LONG datatype, which should not contain unique or primary key constraint.
ii> Column cannot be indexed.
iii> Procedures or stored procedures cannot accept LONG datatype as argument.

-> It can store Numeric data such as Zero, Positive or Negative, Fixed or Floating point data.
-> It accepts Positive and negative integers and real number and has from 1 to 38 digits of precision.
-> Scale which refers to number of digits to the right of the decimal point, which varies between (-84) to 127.
-> Format of declaring NUMBER datatype is NUMBER( Precision, Scale)
1) NUMBER(5) - It can store numeric data upto 5 digits i.e. 99999
2) NUMBER(8,2) - It can store numeric data of 6 Integers and 2 for decimal.
i.e. 999999.99

-> It stores Alphanumeric data values.
-> The field must be between 1 and 2000 characters long.
-> VARCHAR2 supports Oracle built-in functions and operators.
-> It supports a variable length character string.
-> Format of declaring VARCHAR2 IS VARCHAR2( size ).

Same as Varchar2. Always use Varchar2 instead of varchar as it may not be supported in future.

7) BLOB (Binary Large OBjects)
-> Blob include documents, graphics, sound, video, actually any type of binary file you can think of.
-> A binary large object with a limit of 4GB in length.
-> When you want to associate a BLOB with a 'NORMAL' row, two choices are available to you.
i> Store the BLOB in an operating system file(such as an MS-DOS file) and stores the directory and filename in the associated table.
ii> Store the BLOB itself in the LONG RAW column.

8) CLOB (Character Large OBject)
-> A character Large object with a limit of 4GB in length.

-> Boolean variables are used in PL/SQL control structure such as IF-then-ELSE and LOOP statements. A Boolean value can hold true, false or NULL only.

-> It can store binary data upto 2GB.
-> LONG RAW datatype is designed for BLOB storage. You can't use any of the built-in functions with a LONG RAW column.

11) RAW
-> It can store binary data upto 255 bytes.
-> Because of this storing restriction, a RAW column is less useful than a LONG RAW column.

-> Hexadecimal string representing the address of a row in a table.

-> Specifies size of an INTEGER(n) digits wide.

-> The number type is stored in a decimal format which is optimized for accuracy and store efficiency. This datatype is used to store signed integer values, which range from TM2147483647 to +2147483647. It is stored in a 2's complement binary format. Loop Counter are often of type BINARY INTEGER.

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