How do you attach two sqlite db inside a shell script and script operations with their aliases?
for example: from the sqlite3 shell I can attach two different dbs, lets say db1 and db2, and then use:
insert into db2.table1(column1) select column1 from db1.table1;
to copy one column from a specific table on db1 to a specific table on db2.
but, how do I do that same inside a shell script?
To give multiple lines to the input of another program, you could redirect from a temporary file, or from a here document:
sqlite3 "" <<EndOfSqlite3Commands
ATTACH 'database1.db' AS db1;
ATTACH 'database2.db' AS db2;
INSERT INTO db2.table1(column1) SELECT column1 FROM db1.table1;
EndOfSqlite3Commands
Related
I have an SQLite 3 database (db) like in this simplified example:
CREATE TABLE user(id integer primary key, name text);
INSERT INTO "user" VALUES(1,'user1');
INSERT INTO "user" VALUES(2,'user2');
If I enter .dump, sqlite will wrap these statements in a transaction and write them to the file db.sql previously defined with .output. This is fine if I need to import the data to an empty DB.
I want to be able to import the user data to a different DB with other users defined. If I try, I will most likely get something like this (as the ids may be used already in the target DB):
Error: near line 4: PRIMARY KEY must be unique
Error: near line 5: PRIMARY KEY must be unique
My approaches:
I can tweak the dumped SQL manually to remove everything but the inserts and also remove the id column (mentioning only name) in the statement, but this approach does not scale as I want to automate the process.
I can select from the db and write the SQL myself.
Is there any easy or more elegant approach that I am missing? sqlite3 will be run from a Bash script in the real world problem.
You can automate the tweaking (but this still requires that you know the table structure):
$ (echo ".mode insert"; echo "SELECT name FROM user;") | \
sqlite3 my.db | \
sed -e 's/^INSERT INTO table /INSERT INTO user(name) /'
INSERT INTO user(name) VALUES('user1');
INSERT INTO user(name) VALUES('user2');
Is it possible to create an empty sqlite3 database from the command line (e.g. sqlite3 <someoption> dbname) which would create a database file for me empty of any tables so that I can access it from a different SQL editor?
Currently, when I do sqlite3 dbname, I get a sqlite prompt from which I can do CREATE TABLE ... but if I don't, when I exit, no file is created. So I am looking for a single command which would create an empty database for me without a need to create at least one table within that step.
Use the VACUUM command to create a valid empty SQLite database file, including the root database page and the database header.
sqlite3 file.db "VACUUM;"
I don't think there is a way to do that in just one statement.
In Linux I would workaround it this way:
sqlite3 aFile.db "create table aTable(field1 int); drop table aTable;"
This will automatically create the needed file with the table in it and then drop it leaving the database file without tables. That's the closest thing I know.
Anyway, I think most editors will even accept an empty file too. Give that a try.
The simple way is in bash, use command
touch file.db
This will just create a 0 size file and can be used as an empty sqlite file.
You can also call .databases when you enter the command prompt.
Or:
sqlite3 test.db ".databases"
Just create an empty file.
> test.db
Symbol ">" here means redirection.
Creating a blank db like this ( provided by mosty-mostacho ) has an advantage of being recognised as a valid SQLite db; better than an empty file.
$sqlite3 foo.db "create table t(f int); drop table t;"
Verify it by :
$file foo.db
foo.db: SQLite 3.x database, last written using SQLite version 3024000
from https://sqlite.org/cli.html
Start the sqlite3 program by typing "sqlite3" at the command prompt,
optionally followed by the name the file that holds the SQLite
database (or ZIP archive). If the named file does not exist, a new
database file with the given name will be created automatically. If no
database file is specified on the command-line, a temporary database
is created and automatically deleted when the "sqlite3" program exits.
my emphasis
I have a Sqlite database file that i modify it by dropping a huge database table that contains thousands of records but the file size remains as it before dropping the table. it seems that it disconnect pointers to data . any ideas how to drop table and make a deep deletion of it in the underlying sqlite file .??
To reclaim space, use the vacuum statement.
From a sqlite prompt
sqlite> VACUUM;
From a shell prompt.
$ sqlite3 filename 'VACUUM;'
When I was searching for a tool to create and update SQlite databases for use in an Android application I was recommended to use SQLite Database Browser. This has a windows GUI and is reasonably powerful, offering in particular a menu option to import data to a new table from a CSV file.
This has proved perfectly capable for initial creation of the database and I have been using the CSV Import option to update the database whenever I have new data to be added.
When there were only a few records to import this worked well, however as the volume of data has grown the process has become painfully slow. A data file of 11,000 records (800 kilobytes) takes about 10 minutes to import on my averagely slow laptop. Using SQLite Database Browser the whole process of deleting the old table, running the import command, then correcting the data types of the new table created by the import command takes the best part of 15 minutes.
How can the import be speeded up?
You could use the built-in csv import (using the sqlite3 command line utility):
create table test (id integer, value text);
.separator ","
.import no_yes.csv test
Importing 10,000 records took less than 1 second on my Laptop.
By googling I have found several people asking this question, however I have not found the answer set out in once place in simple terms that I could understand. So, I hope the following will help.
The command line utility sqlite3.exe offers a very simple solution. The reason why the "import CSV" option in SQLite Database Browser is so slow is that it executes and commits to the database a separate SQL 'insert' statement foreach line in the CSV file. However, sqlite3.exe includes an "import" command which will process the whole in one go. What's more this is done virtually instantaneously: my 11,000 records are imported in well under a second.
There is a slight drawback in that the import command does not deal with commas in the same way as other programs such as Excel. For example,
if cell A1 in Excel contains Joe Bloggs
and cell B1 contains 123 Main Street, Anytown
the row is exported into a CSV file as:
Joe Bloggs,"123 Main Street, Anytown"
However, if you tried to import this using sqlite3 into a 2-column table, sqlite3 would report an error because it would treat each of the commas as a field separator and so would try to import Joe Bloggs, "123 Main Street and Anytown" as 3 separate fields.
Because it is unusual for text fields (especially in Excel) to include tabs this problem can usually be avoided by using a file where the fields are delimited by tabs rather than by commas.
Since sqlite3.exe can execute any SQL statement and a number of additional commands (like 'import') it is very flexible. However, a routine job like my need to import a delimited data file into a database table can be automated by:
listing the SQL statements and sqlite3.exe commands in a small text file, and feeding this file into sqlite3.exe as a command line parameter
writing a short Windows (MS-DOS) batch file to run sqlite3.exe with the specified list of commands.
These are the steps I followed:
Download and unzip sqlite3.exe
Convert the raw data from comma separated values to tab separated values.
Create a script file listing commands to be executed by sqlite3.exe as follows:
drop table tblTableName;
create table tblTableName(_id INTEGER PRIMARY KEY, fldField1 TEXT, fldField2 NUMERIC, .... );
.mode tabs
.import SubfolderName/DataToBeImported.tsv tblTableName
(Note: SQL statements are followed by a semi-colon; sqlite3.exe commands are preceded by a full stop (period))
Create a .bat file as follows:
cd "c:\users\UserName\FolderWhereSqlite3DatabaseFileAndScriptFileAreStored"
sqlite3 DatabaseName < textimportscript.txt
Having set this up, all I need to do whenever I have new data to add is run the batch file and the data is imported in an instant.
If you are generating INSERT statements, enclose them in a single transaction as stated in the official SQLite FAQ:
BEGIN; -- or BEGIN TRANSACTION;
INSERT ...;
INSERT ...;
END; -- can be COMMIT TRANSACTION; also
Have you tried wrapping all of your updates into a transaction? I had a similar problem and doing that sped it up no end.
Assuming Android Device:
db.beginTransaction();
// YOUR CODE
db.setTransactionSuccessful();
db.endTransaction();
Try that :)
sqlite> PRAGMA journal_mode=WAL;
sqlite> PRAGMA synchronous = 0;
sqlite> PRAGMA journal_mode=MEMORY;
memory
sqlite> BEGIN IMMEDIATE;
.import --csv blah.csv <tablename>
sqlite> COMMIT;
This turns off sync() on write, and puts the WAL file in memory, so it's not "safe", but as long as you are doing this "offline" as it were, and were OK re-creating the DB if power went out, disk gets full, etc, then this will def. speed up the import.
Does anybody have any tips on utilities that can be used to bulk load data that is stored in delimited text files into an SQLite database?
Ideally something that can be called as a stand-alone program from a script etc.
A group I work with has an Oracle Database that's going to dump a bunch of data out to file and then load that data into an SQLite database for use on a mobile device and are looking for the easiest way to implement that sort of scenario.
Check out the sqite .import command - it does exacty this.
You can set the separator with the .separator command
sqlite3 myDatabase
create table myTable (a, b, c);
.separator ','
.import myFile myTable
Why do you want a text file?
Just use Java which does have easily available libraries for Oracle and SQLite access. Connect to both databases and just select from one db and insert into another with no additional complexity of CSV, which is not a very well defined format and will give you problems with character encoding, quotes, comas/tabs or semicolons, newlines etc. in your data.