1.作用
help_category：关于帮助类别的信息。
help_keyword：与帮助主题相关的关键字。
help_relation：帮助关键字与主题之间的映射。
help_topic：帮助主题内容。
在MySQL 5.7.5后，这些表使用InnoDB存储引擎。之前版本使用MyISAM。
2.详解
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| mysql> select * from mysql.help_category;
+------------------+---------------------------------------+--------------------+-----+
| help_category_id | name | parent_category_id | url |
+------------------+---------------------------------------+--------------------+-----+
| 0 | Contents | 0 | |
| 1 | Help Metadata | 0 | |
| 2 | Data Types | 0 | |
| 3 | Administration | 0 | |
| 4 | Procedures | 0 | |
| 5 | Language Structure | 0 | |
| 6 | Geographic Features | 0 | |
| 7 | MBR | 6 | |
| 8 | WKT | 6 | |
| 9 | Functions | 0 | |
| 10 | Comparison Operators | 9 | |
| 11 | Logical Operators | 9 | |
| 12 | Control Flow Functions | 9 | |
| 13 | String Functions | 9 | |
| 14 | Numeric Functions | 9 | |
| 15 | Date and Time Functions | 9 | |
| 16 | Bit Functions | 9 | |
| 17 | Encryption Functions | 9 | |
| 18 | Locking Functions | 9 | |
| 19 | Information Functions | 9 | |
| 20 | Spatial Functions | 9 | |
| 21 | WKT Functions | 20 | |
| 22 | WKB Functions | 20 | |
| 23 | Geometry Constructors | 20 | |
| 24 | Geometry Property Functions | 20 | |
| 25 | Point Property Functions | 20 | |
| 26 | LineString Property Functions | 20 | |
| 27 | Polygon Property Functions | 20 | |
| 28 | GeometryCollection Property Functions | 20 | |
| 29 | Geometry Relation Functions | 20 | |
| 30 | MBR Functions | 20 | |
| 31 | GROUP BY Functions and Modifiers | 9 | |
| 32 | Miscellaneous Functions | 9 | |
| 33 | Data Definition | 0 | |
| 34 | Data Manipulation | 0 | |
| 35 | Transactions | 0 | |
| 36 | Compound Statements | 0 | |
| 37 | Account Management | 0 | |
| 38 | Table Maintenance | 0 | |
| 39 | User-Defined Functions | 0 | |
| 40 | Plugins | 0 | |
| 41 | Utility | 0 | |
| 42 | Storage Engines | 0 | |
+------------------+---------------------------------------+--------------------+-----+
43 rows in set (0.00 sec)
select * from mysql.help_keyword;
select * from mysql.help_relation;
select * from mysql.help_topic\G
|