Rails3でSQLiteを操作する

アプリケーションが登録したデータや、作成されたテーブル情報を参照します。
## SQLite起動
```
$ rails db
SQLite version 3.6.20
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite>
```
## テーブル一覧
```
sqlite> .tables
feedbacks	labels	samples	schema_migrations
```

## スキーマ情報取得
```
sqlite> .schema feedbacks
CREATE TABLE "feedbacks" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "name" varchar(255), "comment" text, "created_at" datetime NOT NULL, "updated_at" datetime NOT NULL);
```

## SQLiteコマンドヘルプ
```
sqlite> .help
.backup ?DB? FILE      Backup DB (default "main") to FILE
.bail ON|OFF           Stop after hitting an error.  Default OFF
.databases             List names and files of attached databases
.dump ?TABLE? ...      Dump the database in an SQL text format
                         If TABLE specified, only dump tables matching
                         LIKE pattern TABLE.
.echo ON|OFF           Turn command echo on or off
.exit                  Exit this program
.explain ON|OFF        Turn output mode suitable for EXPLAIN on or off.
.genfkey ?OPTIONS?     Options are:
                         --no-drop: Do not drop old fkey triggers.
                         --ignore-errors: Ignore tables with fkey errors
                         --exec: Execute generated SQL immediately
                       See file tool/genfkey.README in the source 
                       distribution for further information.
.header(s) ON|OFF      Turn display of headers on or off
.help                  Show this message
.import FILE TABLE     Import data from FILE into TABLE
.indices ?TABLE?       Show names of all indices
                         If TABLE specified, only show indices for tables
                         matching LIKE pattern TABLE.
.load FILE ?ENTRY?     Load an extension library
.mode MODE ?TABLE?     Set output mode where MODE is one of:
                         csv      Comma-separated values
                         column   Left-aligned columns.  (See .width)
                         html     HTML <table> code
                         insert   SQL insert statements for TABLE
                         line     One value per line
                         list     Values delimited by .separator string
                         tabs     Tab-separated values
                         tcl      TCL list elements
.nullvalue STRING      Print STRING in place of NULL values
.output FILENAME       Send output to FILENAME
.output stdout         Send output to the screen
.prompt MAIN CONTINUE  Replace the standard prompts
.quit                  Exit this program
.read FILENAME         Execute SQL in FILENAME
.restore ?DB? FILE     Restore content of DB (default "main") from FILE
.schema ?TABLE?        Show the CREATE statements
                         If TABLE specified, only show tables matching
                         LIKE pattern TABLE.
.separator STRING      Change separator used by output mode and .import
.show                  Show the current values for various settings
.tables ?TABLE?        List names of tables
                         If TABLE specified, only list tables matching
                         LIKE pattern TABLE.
.timeout MS            Try opening locked tables for MS milliseconds
.width NUM NUM ...     Set column widths for "column" mode
.timer ON|OFF          Turn the CPU timer measurement on or off
```

## SQLite終了
```
sqlite> .exit
```