For example, to create a new SQLite database named "ex1"
with a single table named "tbl1", you might do this:
}
proc Code {body} {
puts {You can terminate the sqlite3 program by typing your systems
End-Of-File character (usually a Control-D) or the interrupt
character (usually a Control-C).
Make sure you type a semicolon at the end of each SQL command!
The sqlite3 program looks for a semicolon to know when your SQL command is
complete. If you omit the semicolon, sqlite3 will give you a
continuation prompt and wait for you to enter more text to be
added to the current SQL command. This feature allows you to
enter SQL commands that span multiple lines. For example:
}
Code {
sqlite> (((CREATE TABLE tbl2 ()))
...> ((( f1 varchar(30) primary key,)))
...> ((( f2 text,)))
...> ((( f3 real)))
...> ((();)))
sqlite>
}
puts {
The database schema in an SQLite database is stored in
a special table named "sqlite_master".
You can execute "SELECT" statements against the
special sqlite_master table just like any other table
in an SQLite database. For example:
}
Code {
$ (((sqlite3 ex1)))
SQlite vresion 3.3.10
Enter ".help" for instructions
sqlite> (((select * from sqlite_master;)))
type = table
name = tbl1
tbl_name = tbl1
rootpage = 3
sql = create table tbl1(one varchar(10), two smallint)
sqlite>
}
puts {
But you cannot execute DROP TABLE, UPDATE, INSERT or DELETE against
the sqlite_master table. The sqlite_master
table is updated automatically as you create or drop tables and
indices from the database. You can not make manual changes
to the sqlite_master table.
The schema for TEMPORARY tables is not stored in the "sqlite_master" table
since TEMPORARY tables are not visible to applications other than the
application that created the table. The schema for TEMPORARY tables
is stored in another special table named "sqlite_temp_master". The
"sqlite_temp_master" table is temporary itself.
Most of the time, sqlite3 just reads lines of input and passes them
on to the SQLite library for execution.
But if an input line begins with a dot ("."), then
that line is intercepted and interpreted by the sqlite3 program itself.
These "dot commands" are typically used to change the output format
of queries, or to execute certain prepackaged query statements.
For a listing of the available dot commands, you can enter ".help"
at any time. For example:
}
Code {
sqlite> (((.help)))
.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
.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.
.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 on 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 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
.schema ?TABLE? Show the CREATE statements
.separator STRING Change separator used by output mode and .import
.show Show the current values for various settings
.tables ?PATTERN? List names of tables matching a LIKE pattern
.timeout MS Try opening locked tables for MS milliseconds
.width NUM NUM ... Set column widths for "column" mode
sqlite>
}
puts {
Changing Output Formats
The sqlite3 program is able to show the results of a query
in eight different formats: "csv", "column", "html", "insert",
"line", "tabs", and "tcl".
You can use the ".mode" dot command to switch between these output
formats.
The default output mode is "list". In
list mode, each record of a query result is written on one line of
output and each column within that record is separated by a specific
separator string. The default separator is a pipe symbol ("|").
List mode is especially useful when you are going to send the output
of a query to another program (such as AWK) for additional processing.
}
Code {
sqlite> (((.mode list)))
sqlite> (((select * from tbl1;)))
hello|10
goodbye|20
sqlite>
}
puts {
You can use the ".separator" dot command to change the separator
for list mode. For example, to change the separator to a comma and
a space, you could do this:
}
Code {
sqlite> (((.separator ", ")))
sqlite> (((select * from tbl1;)))
hello, 10
goodbye, 20
sqlite>
}
puts {
In "line" mode, each column in a row of the database
is shown on a line by itself. Each line consists of the column
name, an equal sign and the column data. Successive records are
separated by a blank line. Here is an example of line mode
output:
}
Code {
sqlite> (((.mode line)))
sqlite> (((select * from tbl1;)))
one = hello
two = 10
one = goodbye
two = 20
sqlite>
}
puts {
In column mode, each record is shown on a separate line with the
data aligned in columns. For example:
}
Code {
sqlite> (((.mode column)))
sqlite> (((select * from tbl1;)))
one two
---------- ----------
hello 10
goodbye 20
sqlite>
}
puts {
By default, each column is at least 10 characters wide.
Data that is too wide to fit in a column is truncated. You can
adjust the column widths using the ".width" command. Like this:
}
Code {
sqlite> (((.width 12 6)))
sqlite> (((select * from tbl1;)))
one two
------------ ------
hello 10
goodbye 20
sqlite>
}
puts {
The ".width" command in the example above sets the width of the first
column to 12 and the width of the second column to 6. All other column
widths were unaltered. You can gives as many arguments to ".width" as
necessary to specify the widths of as many columns as are in your
query results.
If you specify a column a width of 0, then the column
width is automatically adjusted to be the maximum of three
numbers: 10, the width of the header, and the width of the
first row of data. This makes the column width self-adjusting.
The default width setting for every column is this
auto-adjusting 0 value.
The column labels that appear on the first two lines of output
can be turned on and off using the ".header" dot command. In the
examples above, the column labels are on. To turn them off you
could do this:
}
Code {
sqlite> (((.header off)))
sqlite> (((select * from tbl1;)))
hello 10
goodbye 20
sqlite>
}
puts {
Another useful output mode is "insert". In insert mode, the output
is formatted to look like SQL INSERT statements. You can use insert
mode to generate text that can later be used to input data into a
different database.
When specifying insert mode, you have to give an extra argument
which is the name of the table to be inserted into. For example:
}
Code {
sqlite> (((.mode insert new_table)))
sqlite> (((select * from tbl1;)))
INSERT INTO 'new_table' VALUES('hello',10);
INSERT INTO 'new_table' VALUES('goodbye',20);
sqlite>
}
puts {
The last output mode is "html". In this mode, sqlite3 writes
the results of the query as an XHTML table. The beginning
<TABLE> and the ending </TABLE> are not written, but
all of the intervening <TR>s, <TH>s, and <TD>s
are. The html output mode is envisioned as being useful for
CGI.
}
puts {
Writing results to a file
By default, sqlite3 sends query results to standard output. You
can change this using the ".output" command. Just put the name of
an output file as an argument to the .output command and all subsequent
query results will be written to that file. Use ".output stdout" to
begin writing to standard output again. For example:
}
Code {
sqlite> (((.mode list)))
sqlite> (((.separator |)))
sqlite> (((.output test_file_1.txt)))
sqlite> (((select * from tbl1;)))
sqlite> (((.exit)))
$ (((cat test_file_1.txt)))
hello|10
goodbye|20
$
}
puts {
Querying the database schema
The sqlite3 program provides several convenience commands that
are useful for looking at the schema of the database. There is
nothing that these commands do that cannot be done by some other
means. These commands are provided purely as a shortcut.
For example, to see a list of the tables in the database, you
can enter ".tables".
}
Code {
sqlite> (((.tables)))
tbl1
tbl2
sqlite>
}
puts {
The ".tables" command is similar to setting list mode then
executing the following query:
SELECT name FROM sqlite_master
WHERE type IN ('table','view') AND name NOT LIKE 'sqlite_%'
UNION ALL
SELECT name FROM sqlite_temp_master
WHERE type IN ('table','view')
ORDER BY 1
In fact, if you look at the source code to the sqlite3 program
(found in the source tree in the file src/shell.c) you'll find
exactly the above query.
The ".indices" command works in a similar way to list all of
the indices for a particular table. The ".indices" command takes
a single argument which is the name of the table for which the
indices are desired. Last, but not least, is the ".schema" command.
With no arguments, the ".schema" command shows the original CREATE TABLE
and CREATE INDEX statements that were used to build the current database.
If you give the name of a table to ".schema", it shows the original
CREATE statement used to make that table and all if its indices.
We have:
}
Code {
sqlite> (((.schema)))
create table tbl1(one varchar(10), two smallint)
CREATE TABLE tbl2 (
f1 varchar(30) primary key,
f2 text,
f3 real
)
sqlite> (((.schema tbl2)))
CREATE TABLE tbl2 (
f1 varchar(30) primary key,
f2 text,
f3 real
)
sqlite>
}
puts {
The ".schema" command accomplishes the same thing as setting
list mode, then entering the following query:
SELECT sql FROM
(SELECT * FROM sqlite_master UNION ALL
SELECT * FROM sqlite_temp_master)
WHERE type!='meta'
ORDER BY tbl_name, type DESC, name
Or, if you give an argument to ".schema" because you only
want the schema for a single table, the query looks like this:
SELECT sql FROM
(SELECT * FROM sqlite_master UNION ALL
SELECT * FROM sqlite_temp_master)
WHERE type!='meta' AND sql NOT NULL AND name NOT LIKE 'sqlite_%'
ORDER BY substr(type,2,1), name
You can supply an argument to the .schema command. If you do, the
query looks like this:
SELECT sql FROM
(SELECT * FROM sqlite_master UNION ALL
SELECT * FROM sqlite_temp_master)
WHERE tbl_name LIKE '%s'
AND type!='meta' AND sql NOT NULL AND name NOT LIKE 'sqlite_%'
ORDER BY substr(type,2,1), name
The "%s" in the query is replace by your argument. This allows you
to view the schema for some subset of the database.
}
Code {
sqlite> (((.schema %abc%)))
}
puts {
Along these same lines,
the ".table" command also accepts a pattern as its first argument.
If you give an argument to the .table command, a "%" is both
appended and prepended and a LIKE clause is added to the query.
This allows you to list only those tables that match a particular
pattern.
The ".databases" command shows a list of all databases open in
the current connection. There will always be at least 2. The first
one is "main", the original database opened. The second is "temp",
the database used for temporary tables. There may be additional
databases listed for databases attached using the ATTACH statement.
The first output column is the name the database is attached with,
and the second column is the filename of the external file.
}
Code {
sqlite> (((.databases)))
}
puts {
Converting An Entire Database To An ASCII Text File
Use the ".dump" command to convert the entire contents of a
database into a single ASCII text file. This file can be converted
back into a database by piping it back into sqlite3.
A good way to make an archival copy of a database is this:
}
Code {
$ (((echo '.dump' | sqlite3 ex1 | gzip -c >ex1.dump.gz)))
}
puts {
This generates a file named ex1.dump.gz that contains everything
you need to reconstruct the database at a later time, or on another
machine. To reconstruct the database, just type:
}
Code {
$ (((zcat ex1.dump.gz | sqlite3 ex2)))
}
puts {
The text format is pure SQL so you
can also use the .dump command to export an SQLite database
into other popular SQL database engines. Like this:
}
Code {
$ (((createdb ex2)))
$ (((sqlite3 ex1 .dump | psql ex2)))
}
puts {
Other Dot Commands
The ".explain" dot command can be used to set the output mode
to "column" and to set the column widths to values that are reasonable
for looking at the output of an EXPLAIN command. The EXPLAIN command
is an SQLite-specific SQL extension that is useful for debugging. If any
regular SQL is prefaced by EXPLAIN, then the SQL command is parsed and
analyzed but is not executed. Instead, the sequence of virtual machine
instructions that would have been used to execute the SQL command are
returned like a query result. For example:
}
Code {
sqlite> (((.explain)))
sqlite> (((explain delete from tbl1 where two<20;)))
addr opcode p1 p2 p3
---- ------------ ----- ----- -------------------------------------
0 ListOpen 0 0
1 Open 0 1 tbl1
2 Next 0 9
3 Field 0 1
4 Integer 20 0
5 Ge 0 2
6 Key 0 0
7 ListWrite 0 0
8 Goto 0 2
9 Noop 0 0
10 ListRewind 0 0
11 ListRead 0 14
12 Delete 0 0
13 Goto 0 11
14 ListClose 0 0
}
puts {
The ".timeout" command sets the amount of time that the sqlite3
program will wait for locks to clear on files it is trying to access
before returning an error. The default value of the timeout is zero so
that an error is returned immediately if any needed database table or
index is locked.
And finally, we mention the ".exit" command which causes the
sqlite3 program to exit.
Using sqlite3 in a shell script
One way to use sqlite3 in a shell script is to use "echo" or
"cat" to generate a sequence of commands in a file, then invoke sqlite3
while redirecting input from the generated command file. This
works fine and is appropriate in many circumstances. But as
an added convenience, sqlite3 allows a single SQL command to be
entered on the command line as a second argument after the
database name. When the sqlite3 program is launched with two
arguments, the second argument is passed to the SQLite library
for processing, the query results are printed on standard output
in list mode, and the program exits. This mechanism is designed
to make sqlite3 easy to use in conjunction with programs like
"awk". For example:
}
Code {
$ (((sqlite3 ex1 'select * from tbl1' |)))
> ((( awk '{printf "| %s | %s\n",$1,$2 }')))
|
| hello | 10
|
| goodbye | 20
$
}
puts {
Ending shell commands
SQLite commands are normally terminated by a semicolon. In the shell
you can also use the word "GO" (case-insensitive) or a slash character
"/" on a line by itself to end a command. These are used by SQL Server
and Oracle, respectively. These won't work in sqlite3_exec(),
because the shell translates these into a semicolon before passing them
to that function.
}
puts {
Compiling the sqlite3 program from sources
The sqlite3 program is built automatically when you compile the
SQLite library. Just get a copy of the source tree, run
"configure" and then "make".
}
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