Frequently Asked Questions - SQL Server Data Types

1.  What's the difference between CHAR and VARCHAR data types and when do I use them?
CHAR and VARCHAR data types are both non-Unicode character data types with a maximum length of 8,000 characters.  The main difference between these 2 data types is that a CHAR data type is fixed-length while a VARCHAR is variable-length.  If the number of characters entered in a CHAR data type column is less than the declared column length, spaces are appended to it to fill up the whole length. Another difference is in the storage size wherein the storage size for CHAR is n bytes while for VARCHAR is the actual length in bytes of the data entered (and not n bytes). You should use CHAR data type when the data values in a column are expected to be consistently close to the same size.  On the other hand, you should use VARCHAR when the data values in a column are expected to vary considerably in size.
2.  What's the difference between NCHAR and NVARCHAR data types and when do I use them?
NCHAR and NVARCHAR data types are both Unicode character data types with a maximum length of 4,000 characters.  The main difference between these 2 data types is that an NCHAR data type is fixed-length while an NVARCHAR is variable-length.  If the number of characters entered in an NCHAR data type column is less than the specified column length, spaces are appended to it to fill up the whole length. Another difference is in the storage size wherein the storage size for NCHAR is two times n bytes while for NVARCHAR is two times the number of characters entered (in bytes). You should use NCHAR data type when the data values in a column are expected to be consistently close to the same size.  On the other hand, you should use NVARCHAR when the data values in a column are expected to vary considerably in size.
3.  What's the difference between CHAR and NCHAR data types and when do I use them?
CHAR and NCHAR data types are both character data types that are fixed-length.  Below is the summary of the differences between these 2 data types:   CHAR(n) NCHAR(n) Character Data Type Non-Unicode Data Unicode Data Maximum Length 8,000 4,000 Character Size 1 byte 2 bytes Storage Size n bytes 2 times n bytes You would use NCHAR data type for columns that store characters from more than one character set or when you will be using characters that require 2-byte characters, which are basically the Unicode characters such as the Japanese Kanji or Korean Hangul characters.
4.  What's the difference between VARCHAR and NVARCHAR data types and when do I use them?
VARCHAR and NVARCHAR data types are both character data types that are variable-length.  Below is the summary of the differences between these 2 data types:   VARCHAR(n) NVARCHAR(n) Character Data Type Non-Unicode Data Unicode Data Maximum Length 8,000 4,000 Character Size 1 byte 2 bytes Storage Size Actual Length (in bytes) 2 times Actual Length (in bytes) You would use NVARCHAR data type for columns that store characters from more than one character set or when you will be using characters that require 2-byte characters, which are basically the Unicode characters such as the Japanese Kanji or Korean Hangul characters.
5. What's the difference between TINYINT, SMALLINT, INT and BIGINT data types and when do I use them?					http://www.sql-server-helper.com/faq/data-types-p01.aspx