Char DataType
Char datatype which is used to store fixed length of characters. Suppose if we declared char(50) it will allocates memory for 50 characters. Once we declare char(50) and insert only 10 characters of word then only 10 characters of memory will be used and other 40 characters of memory will be wasted.
varchar DataType
Varchar means variable characters and it is used to store non-unicode characters. It will allocate the memory based on number characters inserted. Suppose if we declared varchar(50) it will allocates memory of 0 characters at the time of declaration. Once we declare varchar(50) and insert only 10 characters of word it will allocate memory for only 10 characters.
nvarchar DataType
nvarchar datatype same as varchar datatype but only difference nvarchar is used to store Unicode characters and it allows you to store multiple languages in database. nvarchar datatype will take twice as much space to store extended set of characters as required by other languages.
So if we are not using other languages then it’s better to use varchar datatype instead of nvarchar
Difference between bit tinyint smallint int and bigint datatypes in SQL Server
Bit DataType
This datatype represents a single bit that can be 0 or 1.
tinyint DataType
This datatype represents a single byte which is used to store values from 0 to 255 (MinVal: 0, MaxVal: 255). Its storage size is 1 byte.
smallint DataType
This datatype represents a signed 16-bit integer which is used to store values from -2^15 (-32,768) through 2^15 - 1 (32,767) and its storage size is 2 bytes.
int DataType
This datatype represents a signed 32-bit integer which is used to store values from -2^31(-2,147,483,648) to 2 ^31-1(2,147,483,647). Its storage size is 4 bytes.
Bigint DataType
This datatype represents a signed 64-bit integer which is used to store values from -2^63 (-9223372036854775808) through 2^63-1 (9223372036854775807). Its storage size is 8 bytes.
