MySQL data type and some useful commands

NUMBER TYPES

TINYINT( )	-128 to 127 normal 0 to 255 UNSIGNED.
SMALLINT( )	-32768 to 32767 normal 0 to 65535 UNSIGNED.
MEDIUMINT( )	-8388608 to 8388607 normal 0 to 16777215 UNSIGNED.
INT( )	-2147483648 to 2147483647 normal 0 to 4294967295 UNSIGNED.
BIGINT( )	-9223372036854775808 to 9223372036854775807 normal 0 to 18446744073709551615 UNSIGNED.
FLOAT	A small number with a floating decimal point.
DOUBLE( , )	A large number with a floating decimal point.
DECIMAL( , )	A DOUBLE stored as a string , allowing for a fixed decimal point.

TEXT TYPES

CHAR( )	A fixed section from 0 to 255 characters long.
VARCHAR( )	A variable section from 0 to 255 characters long.
TINYTEXT	A string with a maximum length of 255 characters.
TEXT	A string with a maximum length of 65535 characters.
BLOB	A string with a maximum length of 65535 characters.
MEDIUMTEXT	A string with a maximum length of 16777215 characters.
MEDIUMBLOB	A string with a maximum length of 16777215 characters.
LONGTEXT	A string with a maximum length of 4294967295 characters.
LONGBLOB	A string with a maximum length of 4294967295 characters.

DATE TYPES

DATE	YYYY-MM-DD.
DATETIME	YYYY-MM-DD HH:MM:SS.
TIMESTAMP	YYYYMMDDHHMMSS.
TIME	HH:MM:SS.

MISC TYPES

ENUM ( )	Short for ENUMERATION which means that each column may have one of a specified possible values.
SET	Similar to ENUM except each column may have more than one of the specified possible values.

Counting Rows

SELECT COUNT(*) FROM pet;
SELECT owner, COUNT(*) FROM pet GROUP BY owner;

SELECT COUNT(score) AS n,
    -> SUM(score) AS sum,
    -> MIN(score) AS minimum,
    -> MAX(score) AS maximum,
    -> AVG(score) AS mean,
    -> STD(score) AS 'std. dev.'
    -> FROM testscore;