Learning PHP-MySQL基础知识

引用

关系数据库中有三种基本的关系类型。根据关系双方所含对象的多少，可以将这些关系氛围一对一、一对多、多对多三种关系。

最少权限原则：
一个用户（或者一个进程）应该拥有能够执行分配给他的任务的最低级别的权限。
创建用户：GRANT命令
GRANT和REVOKE命令分别用来授予和取消MySQL用户的权限，这些权限分四个级别。他们分别是：

• 全局
• 数据库
• 表
• 列

mysql> help grant;
Name: 'GRANT'
Description:
Syntax:
GRANT
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    ON [object_type] priv_level
    TO user_specification [, user_specification] ...
    [REQUIRE {NONE | ssl_option [[AND] ssl_option] ...}]
    [WITH with_option ...]

GRANT PROXY ON user_specification
    TO user_specification [, user_specification] ...
    [WITH GRANT OPTION]

object_type:
    TABLE
  | FUNCTION
  | PROCEDURE

priv_level:
    *
  | *.*
  | db_name.*
  | db_name.tbl_name
  | tbl_name
  | db_name.routine_name

user_specification:
    user
    [
        IDENTIFIED BY [PASSWORD] 'password'
      | IDENTIFIED WITH auth_plugin [AS 'auth_string']
    ]

ssl_option:
    SSL
  | X509
  | CIPHER 'cipher'
  | ISSUER 'issuer'
  | SUBJECT 'subject'

with_option:
    GRANT OPTION
  | MAX_QUERIES_PER_HOUR count
  | MAX_UPDATES_PER_HOUR count
  | MAX_CONNECTIONS_PER_HOUR count
  | MAX_USER_CONNECTIONS count

The GRANT statement grants privileges to MySQL user accounts. GRANT
also serves to specify other account characteristics such as use of
secure connections and limits on access to server resources. To use
GRANT, you must have the GRANT OPTION privilege, and you must have the
privileges that you are granting.

Normally, a database administrator first uses CREATE USER to create an
account, then GRANT to define its privileges and characteristics. For
example:

CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'mypass';
GRANT ALL ON db1.* TO 'jeffrey'@'localhost';
GRANT SELECT ON db2.invoice TO 'jeffrey'@'localhost';
GRANT USAGE ON *.* TO 'jeffrey'@'localhost' WITH MAX_QUERIES_PER_HOUR 90;

However, if an account named in a GRANT statement does not already
exist, GRANT may create it under the conditions described later in the
discussion of the NO_AUTO_CREATE_USER SQL mode.

The REVOKE statement is related to GRANT and enables administrators to
remove account privileges. See [HELP REVOKE].

When successfully executed from the mysql program, GRANT responds with
Query OK, 0 rows affected. To determine what privileges result from the
operation, use SHOW GRANTS. See [HELP SHOW GRANTS].

URL: http://dev.mysql.com/doc/refman/5.5/en/grant.html

REVOKE命令
与GRANT相反的命令。用来从一个用户收回权限。

mysql> help revoke;
Name: 'REVOKE'
Description:
Syntax:
REVOKE
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    ON [object_type] priv_level
    FROM user [, user] ...

REVOKE ALL PRIVILEGES, GRANT OPTION
    FROM user [, user] ...

REVOKE PROXY ON user
    FROM user [, user] ...

The REVOKE statement enables system administrators to revoke privileges
from MySQL accounts. Each account name uses the format described in
http://dev.mysql.com/doc/refman/5.5/en/account-names.html. For example:

REVOKE INSERT ON *.* FROM 'jeffrey'@'localhost';

If you specify only the user name part of the account name, a host name
part of '%' is used.

For details on the levels at which privileges exist, the permissible
priv_type and priv_level values, and the syntax for specifying users
and passwords, see [HELP GRANT]

To use the first REVOKE syntax, you must have the GRANT OPTION
privilege, and you must have the privileges that you are revoking.

To revoke all privileges, use the second syntax, which drops all
global, database, table, column, and routine privileges for the named
user or users:

REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ...

To use this REVOKE syntax, you must have the global CREATE USER
privilege or the UPDATE privilege for the mysql database.

URL: http://dev.mysql.com/doc/refman/5.5/en/revoke.html

例子：

mysql > grant all on * to eric identified by '123456' with grant option;
mysql > revode all privileges, grant from eric;

创建一个没有任何权限的常规用户：

mysql > grant usage on books.* to sally identified by '123456';

授予权限

mysql > grant select,insert,update,delete,index,alter,create,drop on books.* to sally;

收回权限

mysql > revoke alter,create,drop on books.* from sally;
mysql > revoke all on books.* from sally;

创建一个Web用户
授予增删改查的权限

mysql > grant select,insert,delete,update on books.* to user_a identified by '123456';

创建索引：

mysql> help create index;
Name: 'CREATE INDEX'
Description:
Syntax:
CREATE [ONLINE|OFFLINE] [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name
    [index_type]
    ON tbl_name (index_col_name,...)
    [index_option] ...

index_col_name:
    col_name [(length)] [ASC | DESC]

index_type:
    USING {BTREE | HASH}

index_option:
    KEY_BLOCK_SIZE [=] value
  | index_type
  | WITH PARSER parser_name
  | COMMENT 'string'

CREATE INDEX is mapped to an ALTER TABLE statement to create indexes.
See [HELP ALTER TABLE]. CREATE INDEX cannot be used to create a PRIMARY
KEY; use ALTER TABLE instead. For more information about indexes, see
http://dev.mysql.com/doc/refman/5.5/en/mysql-indexes.html.

URL: http://dev.mysql.com/doc/refman/5.5/en/create-index.html

SQL是什么
SQL全称是Structured Query Language。
表关联的总结
MySQL中的关联类型
名称                   描述

• 笛卡尔儿乘积       所有表所有行的所有关联。实现方法，在列的名称之间指定一个逗号，而            
                             不是指定一个WHERE字句。  
• 完全关联             同上
• 交叉关联             同上，也可以通过在关联的表明之间指定CROSS JOIN关键词的指定。
• 内部关联             如果没有WHERE条件，等价于完全关联。
• 等价关联             在关联中使用一个带“=”号的条件表达式匹配来自不同表中的行。
• 左关联               试图匹配表的行并在不匹配的行中填入NULL，在SQL中使用LEFT JOIN关键词。

参考资料：
PHP&MySQL.Web