Database Storage allocation/Choosing Right Column Types mysql

Here integer type along with minimum maximum value length and storage in byte.

Type	Storage	Minimum Value	Maximum Value
	(Bytes)	(Signed/Unsigned)	(Signed/Unsigned)
TINYINT	1	-128	127
		0	255
SMALLINT	2	-32768	32767
		0	65535
MEDIUMINT	3	-8388608	8388607
		0	16777215
INT	4	-2147483648	2147483647
		0	4294967295
BIGINT	8	-9223372036854775808	9223372036854775807
		0	18446744073709551615

In contrast to CHAR (0 to 65,535),  VARCHAR (length 0 to 65,535) values are stored as a 1-byte or 2-byte length prefix plus data. The length prefix indicates the number of bytes in the value. A column uses one length byte if values require no more than 255 bytes, two length bytes if values may require more than 255 bytes.

Value	CHAR(4)	Storage Required	VARCHAR(4)	Storage Required
''	'    '	4 bytes	''	1 byte
'ab'	'ab  '	4 bytes	'ab'	3 bytes
'abcd'	'abcd'	4 bytes	'abcd'	5 bytes
'abcdefgh'	'abcd'	4 bytes	'abcd'	5 bytes

varchar = 1 byte which is fix + number of characters( 0 to 255) byte
varch = 1+4 = 5 byte (abcd is 4 character+1 = 5 byte)
varchar = 2 byte which is fix + number of characters(256 to 65535) byte

For more text type :

TEXT	String length + 2 bytes	A string with a maximum length of 65,535 characters
MEDIUMTEXT	String length + 3 bytes	A string with a maximum length of 16,777,215 characters
LONGTEXT	String length + 4 bytes	A string with a maximum length of 4,294,967,295 characters

For other field/column type

FLOAT[Length, Decimals]	4 bytes	A small number with a floating decimal point
DOUBLE[Length, Decimals]	8 bytes	A large number with a floating decimal point
DECIMAL[Length, Decimals]	Length + 1 or 2 bytes	A DOUBLE stored as a string, allowing for a fixed decimal point
DATE	3 bytes	In the format of YYYY-MM-DD
DATETIME	8 bytes	In the format of YYYY-MM-DD HH:MM:SS
TIMESTAMP	4 bytes	In the format of YYYYMMDDHHMMSS; acceptable range starts in 1970 and ends in the year 2038
TIME	3 bytes	In the format of HH:MM:SS