Sqlite 简明教程

SQLite - Commands

本章将带您了解 SQLite 程序员使用的简单且有用的命令。这些命令称为 SQLite 点命令，而且这些命令的例外之处是它们不应该以分号 (;) 结束。

This chapter will take you through simple and useful commands used by SQLite programmers. These commands are called SQLite dot commands and exception with these commands is that they should not be terminated by a semi-colon (;).

让我们从在命令提示符中输入一个 sqlite3 命令开始，该命令会为您提供 SQLite 命令提示符，您可以在其中发出各种 SQLite 命令。

Let’s start with typing a simple sqlite3 command at command prompt which will provide you with SQLite command prompt where you will issue various SQLite commands.

$sqlite3
SQLite version 3.3.6
Enter ".help" for instructions
sqlite>

您可以随时输入 “.help” 来获取可用点命令的列表。例如−

For a listing of the available dot commands, you can enter ".help" any time. For example −

sqlite>.help

上述命令将显示一个包含各种重要 SQLite 点命令的列表，这些命令列在以下表格中。

The above command will display a list of various important SQLite dot commands, which are listed in the following table.

Sr.No.	Command & Description
1	.backup ?DB? FILE Backup DB (default "main") to FILE
2	*.bail ON
OFF* Stop after hitting an error. Default OFF	3
.databases List names and files of attached databases	4
.dump ?TABLE? Dump the database in an SQL text format. If TABLE specified, only dump tables matching LIKE pattern TABLE	5
*.echo ON	OFF* Turn command echo on or off
6	.exit Exit SQLite prompt
7	*.explain ON
OFF* Turn output mode suitable for EXPLAIN on or off. With no args, it turns EXPLAIN on	8
*.header(s) ON	OFF* Turn display of headers on or off
9	.help Show this message
10	.import FILE TABLE Import data from FILE into TABLE
11	.indices ?TABLE? Show names of all indices. If TABLE specified, only show indices for tables matching LIKE pattern TABLE
12	.load FILE ?ENTRY? Load an extension library
13	*.log FILE
off* Turn logging on or off. FILE can be stderr/stdout	14
.mode MODE Set output mode where MODE is one of − csv − Comma-separated values column − Left-aligned columns. 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	15
.nullvalue STRING Print STRING in place of NULL values	16
.output FILENAME Send output to FILENAME	17
.output stdout Send output to the screen	18
.print STRING… Print literal STRING	19
.prompt MAIN CONTINUE Replace the standard prompts	20
.quit Exit SQLite prompt	21
.read FILENAME Execute SQL in FILENAME	22
.schema ?TABLE? Show the CREATE statements. If TABLE specified, only show tables matching LIKE pattern TABLE	23
.separator STRING Change separator used by output mode and .import	24
.show Show the current values for various settings	25
*.stats ON	OFF* Turn stats on or off
26	.tables ?PATTERN? List names of tables matching a LIKE pattern
27	.timeout MS Try opening locked tables for MS milliseconds
28	.width NUM NUM Set column widths for "column" mode
29	*.timer ON

让我们尝试 .show 命令，以查看 SQLite 命令提示符的默认设置。

Let’s try .show command to see default setting for your SQLite command prompt.

sqlite>.show
     echo: off
  explain: off
  headers: off
     mode: column
nullvalue: ""
   output: stdout
separator: "|"
    width:
sqlite>

确保 sqlite> 提示符和 dot 命令之间没有空格，否则将不起作用。

Make sure there is no space in between sqlite> prompt and dot command, otherwise it will not work.

Formatting Output

您可以使用以下 dot 命令序列来格式化输出。

You can use the following sequence of dot commands to format your output.

sqlite>.header on
sqlite>.mode column
sqlite>.timer on
sqlite>

以上设置将按以下格式生成输出。

The above setting will produce the output in the following format.

ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0
6           Kim         22          South-Hall  45000.0
7           James       24          Houston     10000.0
CPU Time: user 0.000000 sys 0.000000

The sqlite_master Table

master 表保存有关数据库表的关键信息，称为 sqlite_master 。您可以按如下方式查看其架构 −

The master table holds the key information about your database tables and it is called sqlite_master. You can see its schema as follows −

sqlite>.schema sqlite_master

这将产生以下结果。

This will produce the following result.

CREATE TABLE sqlite_master (
   type text,
   name text,
   tbl_name text,
   rootpage integer,
   sql text
);