PHP mobile internet development notes (6) Basic MySQL database review _ MySQL

PHP mobile internet development notes (6) -- MySQL database basic review recently read some architecture materials, but found that the basic knowledge is not very strong. for the next time, I will summarize the basic knowledge on a regular basis.

I. Data types

1. integer

Data type	Storage space	Description	Value range
TINYINT	1 byte	Very small integer	Signed value:-128 ~ 127 Unsigned value: 0 ~ 255
SMALLINT	2 bytes	Small integer	Signed value:-32768 ~ 32767 Unsigned value: 0 ~ 65535
MEDIUMNT	3 bytes	An integer of medium size	Signed value:-8388608 ~ 8388607 Unsigned value: 0 ~ 16777215
INT	4 bytes	Standard integer	Signed value:-2147483648 ~ 2147483647 Unsigned value: 0 ~ 4294967295
BIGINT	8 bytes	Big integer

2. Floating point

Data type	Storage space	Description	Value range
FLOAT	4 bytes	But the precision floating point number
DOUBLE	8 bytes	Double-precision floating point number
DECIMAL (M, D)	Custom	In string format

3. string type

Type	Storage space	Description	Maximum length
Char [(M)]	MB bytes	Fixed length string	MB bytes
Varchar [(M)]	L + 1 byte	Variable length string	MB bytes
Tinyblog, tingtext	L + 1 byte	Very small blob and text string	2 ^ 8 characters
Blog, text	L + 2 bytes	Small BLOB and text string	2 ^ 16-1 bytes
Mediumblob, mediumtext	L + 3 bytes	Moderate BLOB and text string	2 ^ 24 bytes
Longblob, longtext	L + 4 bytes	Large BLOB and text string	2 ^ 32-1 bytes
Enum ('value', 'value ')	1 or 2 bytes	Enumeration: you can assign an enumeration member.	65535 members
Set ('value', 'value ')	1, 2, 3, 4, or 8 bytes	Set: you can assign multiple set members.	64 members

4. date and time data

Type	Storage space	Description	Maximum length
Date	3 bytes	YYYY-MM-DD format representation	1000-01-01 ~ 9999-12-31
TIME	3 bytes	Hh: mm: ss format indicates the time value	-838: 59: 59 ~ 838: 59: 59
DATETIME	8 bytes	YYYY-MM-DD hh: mm: ss format
TIMESTAMP	4 bytes	The format of YYYYMMDDhhmmss indicates the timestamp.
YEAR	1 byte	Year value in YYYY format	1901 ~ 2155

II. MySQL database operations

1. log on to the database

Mysql parameters

-D, -- database = name: Open the specified database

-- Delimiter = name specifies the delimiter

-E, -- vertical display result

-H, -- host = name server name

-H, -- html provides HTML output

-X, -- xml provides XML output

-P, -- password [= name] password

-P, -- port = # port number

-- Prompt = name: Set the prompt

-U, -- user = name username

-V, -- version: Output version information and exit

Mysql-h server host address-u user name-p user password

2. log out

Exit

Quit

/Q

3. change the password

4. create, select, and view databases

Create a database

Select database

Delete database content