markdown MySQL的のヘルプの使い方

Posted 2021-05-05

# MySQLのヘルプの使い方

## とりあえず最初のhelpを表示する
``` mysql
mysql> help

For information about MySQL products and services, visit:
   http://www.mysql.com/
...

-- help contents を入力しろと言われたので、そのとおりにする
For server side help, type 'help contents'
```


## help contents でヘルプのカテゴリ一覧を表示する
``` mysql
mysql> help contents
You asked for help about help category: "Contents"
For more information, type 'help <item>', where <item> is one of the following
categories:
   Account Management
   Administration -- データベースの管理や操作などはここに含まれる
   Components
   ...
```

## help Administration を実行してみる
``` mysql
mysql> help Administration
You asked for help about help category: "Administration"
For more information, type 'help <item>', where <item> is one of the following
topics:
   BINLOG
   CACHE INDEX
   FLUSH
   ...
   SHOW COLUMNS -- テーブル定義を見るコマンドのヘルプ
   ...
```


## help SHOW COLUMNS を実行してみる
``` mysql
mysql> help SHOW COLUMNS
Name: 'SHOW COLUMNS'
Description:
Syntax:
SHOW [EXTENDED] [FULL] {COLUMNS | FIELDS}
    {FROM | IN} tbl_name
    [{FROM | IN} db_name]
    [LIKE 'pattern' | WHERE expr]
...
```

## ヘルプに書かれたとおりにコマンドを実行してみる
``` mysql
mysql> SHOW TABLES;
+-------------------+
| Tables_in_sandbox |
+-------------------+
| users             |
+-------------------+
1 row in set (0.00 sec)

mysql> SHOW COLUMNS FROM users;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| id    | int(10)     | NO   | PRI | NULL    | auto_increment |
| name  | varchar(64) | NO   |     | NULL    |                |
+-------+-------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
```