How to Install and Basic SQLite Use on Linux

sqlite linuxIn this article, We will see how to install SQLite (relational database) with its basic operations. What if I tell you that SQLite is likely used more than all other database engines combined. Yes, You heard it right. It is the most widely deployed database in the world with millions and billions of copies.

The reason behind this popularity is some unique characteristics that are unusual and which makes it different from many other SQL database engines like MySQL, PostgreSQL, Oracle, Microsoft SQL Server, etc. Let's get started with it. First, We will install it on Linux and later on cover basic database operations.

Installing Sqlite

  • To install on your debian based(Ubuntu, Debian etc.) machine execute below commands.
$ sudo apt-get update
$ sudo apt-get install sqlite3
  • To install on your RPM based(RHEL, CentOS, Fedora etc.) machine execute below commands.
$ sudo yum update
$ sudo yum install sqlite

Now Open a terminal and Execute "sqlite3", you will see the following lines with prompt.

$ sqlite3
SQLite version 3.8.2 2013-12-06 14:53:30
Enter ".help" for instructions
Enter SQL statements terminated with a ";"

The very first line shows the version and release date and time of sqlite3.
The second line tells to enter ".help" for instructions.

.help command list all the meta commands and their descriptions. These meta commands are also called "dot" commands because they are preceded by a dot.
Put ".help" to prompt

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.
                         With no args, it turns EXPLAIN on.
.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
.log FILE|off          Turn logging on or off.  FILE can be stderr/stdout
.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      Use STRING in place of NULL values
.open ?FILENAME?       Close existing database and reopen FILENAME
.output FILENAME       Send output to FILENAME
.output stdout         Send output to the screen
.print STRING...       Print literal STRING
.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
.stats ON|OFF          Turn stats on or off
.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
.trace FILE|off        Output each SQL statement as it is run
.vfsname ?AUX?         Print the name of the VFS stack
.width NUM1 NUM2 ...   Set column widths for "column" mode
.timer ON|OFF          Turn the CPU timer measurement on or off

Before explaining these dot commands, let's see some of the basic database operations.
First run ".quit" command to end the session.

Create Database

Execute below command on shell prompt.
It will create "example.db" (You can put your choice of name in place of "example.db") database file ( if not exists). If exists then open the database contained in the file.

$ sqlite3 example.db
SQLite version 3.8.2 2013-12-06 14:53:30
Enter ".help" for instructions
Enter SQL statements terminated with a ";"

The difference between "sqlite3" and "sqlite3 dbname.db" command is the first one will create a temporary database for the session and will expire when the session is closed.

Create Table

Let's create a student table with attributes:

reg_no int(4)
Name varchar(20)
Marks int(3)

enter the following commands in terminal

sqlite> create table student (
   ...> reg_no int(4),
   ...> name   varchar(20),
   ...> marks  int(3)
   ...> );

It will create a student table with above attributes.

You can see the list of tables in the selected database by .table command

sqlite> .table
student

There is only one table student in my case.

You can also see the schema of the table using .schema table_name

sqlite> .schema student
CREATE TABLE student (
reg_no int(4),
name   varchar(20),
marks  int(3)
);

Inserting Data

Let's insert 3 records in the table
101, pradip, 87
102, Avinash, 86
103, Rakesh, 90

Enter following command one by one

sqlite> insert into student (reg_no, name, marks) values (101, 'Pradip', 87);
> insert into student (reg_no, name, marks) values (102, 'Avinash', 86);
> insert into student (reg_no, name, marks) values (103, 'Rakesh', 91);

Fetching data

You can fetch data from table with select statement

sqlite> select * from student;
101|Pradip|87
102|Avinash|86
103|Rakesh|91

It shows the result in default mode (list).

You can change the mode with .mode command

Enter .mode column to prompt and then perform select query. It will show the result in a column format.

sqlite> .mode column
> select * from student;
reg_no      name        marks     
----------  ----------  ----------
101         Pradip      87        
102         Avinash     86        
103         Rakesh      91        

Delete, Alter, Drop etc have same syntax as sql.

Special commands to sqlite3(dot -commands)

we saw ".help" commands list all the dot commands.
Let's understand some other important commands.

  • .databases

Shows name of database selected.

sqlite> .database
seq  name             file                                                      
---  ---------------  --------------------
0    main             /home/avi/example.db
  • .table

List the tables in the selected database.

sqlite> .table
student
  • .show

Shows the current settings

sqlite> .show
     echo: off
  explain: off
  headers: off
     mode: list
nullvalue: ""
   output: stdout
separator: "|"
    stats: off
    width: 
    • .header ON|OFF
      You can show attribute name in query result by running .header ON|OFF command

      sqlite> .header ON
      > select * from student;
      reg_no      name        marks     
      ----------  ----------  ----------
      101         Pradip      87        
      102         Avinash     86        
      103         Rakesh      91        
      
    • .mode

The Program is able to show the results of a query in eight different formats: "csv", "column","html","insert", "line", "list", "tabs", "tcl"..mode command is use to switch between these output formats.

sqlite> .mode csv
> select * from student;
reg_no,name,marks
101,Pradip,87
102,Avinash,86
103,Rakesh,91

You can use .separator command to change separator.

sqlite> .separator -
> select * from student;
reg_no-name-marks
101-Pradip-87
102-Avinash-86
103-Rakesh-91

Writing results to a file

by default, It sends query results to standard output.
you can change this using ".output" and ".once" commands.

Just put the name of an output file as an argument to .output and all subsequent query results will be written to that file.

sqlite> .output ex.txt

Or use the .once the command with file name if you want only the result of next query to be redirected.

We have successfully installed SQLite on Linux with basic operations. These operations are only a few out of all available. We can't cover all of them in this article. If you find any difficulties in an installation or in any command, Let me know in comment section. See you in next article.

About Pradip Sakhavala

Pradip is a Linux system administrator, an ardent believer in sharing and contributing to open source community. He has a keen interest in DevOps And IoT. He likes to discuss technical stuff anytime. He has started sharing his experience by blogs recently.

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