add mysql permission

cspell_dict_bash.txt

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 baseband
 unicast
 multicast
-CSMA
+CSMA
+
+priv

docs/source/reference/database/mysql/mysql-privilege.md

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+# MySQL Privilege
+
+## Why Privilege
+
+Access Control is indispensable.
+
+1. whether or not a user is allowed to connect
+2. whether or not a user can perform the intended action
+
+## Levels
+
+From [MySQL :: MySQL 8.0 Reference Manual :: 13.7.1.6 GRANT Syntax](https://dev.mysql.com/doc/refman/8.0/en/grant.html)
+
+1. Global
+2. Database
+3. Table
+4. Column
+5. Procedure
+
+(6.Proxy)
+
+```sql
+priv_level: {
+    *
+  | *.*
+  | db_name.*
+  | db_name.tbl_name
+  | tbl_name
+  | db_name.routine_name
+}
+```
+
+Flexible
+
+## Commands
+
+`GRANT`
+
+```sql
+GRANT ALL PRIVILEGES ON <some_level> TO <some_user>@<some_host> IDENTIFIED BY <some_password>;
+
+GRANT ALL PRIVILEGES ON *.* TO 'me'@'%' IDENTIFIED BY 'MyPass';
+GRANT ALL PRIVILEGES ON MyDB.* TO 'you'@'%' IDENTIFIED BY 'YourPass';
+GRANT ALL PRIVILEGES ON MyDB.* TO 'another_user_can_grant_permissions'@'localhost' WITH GRANT OPTION;
+
+GRANT SELECT ON YourDB.* TO 'role3';
+```
+
+[About 'Identified By Password - StackOverflow'](https://stackoverflow.com/questions/31111847/identified-by-password-in-mysql)
+
+The "host" is the allowed connection source.
+
+* `*@localhost`
+  * means only connection from localhost are allowed
+* `@%`
+  * means any source is allowed
+* `one.such.domain`
+  * specify a domain
+* `*.such.domain`
+  * use wildcard
+* `0.0.0.0`
+  * specify an ip
+* `192.168.1.9/255.255.255.0`
+  * specify a segment
+
+`REVOKE`
+
+```sql
+REVOKE ALL PRIVILEGES FROM user [, user]…
+REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user]…
+```
+
+## Connection Authorization
+
+In order to perform an action, a user must
+
+* connected from specific source
+* exist (has a record in mysql)
+* give correct authentication credential
+* has permission to perform that action on the target
+
+By default, `root` cannot be accessed from connections other than localhost.
+
+Usually we create a specific database and assign the permissions on that database.