What is char, var, nchar , nvarchar

CHAR vs VARCHAR

CHAR:

• It is a fixed length data type
• Used to store non-Unicode characters
• Occupiers 1 byte of space for each character

1. DECLARE @string CHAR(20)  
2. SET @string = 'Robin'  
3. SELECT @string AS 'String', DATALENGTH(@string) AS 'Datalength' , LEN(@string) AS 'Len' 

VARCHAR:

• It is a variable length data type
• Used to store non-Unicode characters
• Occupies 1 byte of space for each character

1. DECLARE @string VARCHAR(20)  
2. SET @string = 'Robin'  
3. SELECT @string AS 'String', DATALENGTH(@string) AS 'Datalength' , LEN(@string) AS 'Len' 

NCHAR:

• Is a fixed length data type
• Used to store Unicode characters (for example the languages Arabic, German and so on)
• Occupies 2 bytes of space for each character

1. DECLARE @string NCHAR(20)  
2. SET @string = 'Robin'  
3. SELECT @string AS 'String', DATALENGTH(@string) AS 'Datalength' , LEN(@string) AS 'Len' 

 

NVARCHAR:

• It is a variable-length data type
• Used to store Unicode characters
• Occupies 2 bytes of space for each character

1. DECLARE @string NVARCHAR(20)  
2. SET @string = 'Robin'  
3. SELECT @string AS 'String', DATALENGTH(@string) AS 'Datalength' , LEN(@string) AS 'Len' 

When to use what?

If your column will store a fixed-length Unicode characters like French, Arabic and so on characters then go for NCHAR. If the data stored in a column is Unicode and can vary in length, then go for NVARCHAR. 

 

Querying to NCHAR or NVARCHAR is a bit slower then CHAR or VARCHAR. So don't go for NCHAR or NVARCHAR to store non-Unicode characters even though this data type supports that.