I have created a database "MyDB.sqlite" using the command line sqlite3 MyDB.sqlite in a specific folder(my desktop) and then created a table "tbl11" using create table syntax. I am able to insert record and can check the inserted records.
But when I exit command (terminal in Mac) line and re enter I can't see my database and tables in that folder. I guess this database and table are temporary by default. I even check the .databases command to see the database, but I can only see two database main!
please help!
Be sure to finish off with COMMIT; :-)
For practice, work through the short working example at http://souptonuts.sourceforge.net/readme_sqlite_tutorial.html
Good luck.
Related
I have an Ionic App using SQLite. I don't have any problems with implementation.
The issue is that I need to import an SQL file using SQLitePorter to populate the database with configuration info.
But also, on the same database I have user info, so my question is:
Everytime I start the app, it will import the sql file, fill the database and probably overwrite my user data too? Since it is all on the same base?
I assume that you can always init your table using string queries inside your code. The problem is not that you are importing a .sql file. Right?
According to https://www.sqlitetutorial.net/sqlite-create-table/ it is obvious that you always create a table with [IF NOT EXISTS] switch. Writing a query like :
CREATE TABLE [IF NOT EXISTS] [schema_name].table_name (
column_1 data_type PRIMARY KEY);
you let sqlite to decide if it's going to create a table with the risk to overwrite an existing table. It is supposed that you can trust that sqlite is smart enough, not to overwrite any information especially if you use 'BEGIN TRANSACTION' - 'COMMIT' procedure.
I give my answer assuming that you have imported data and user data in distinct tables, so you can manipulate what you populate and what you don't. Is that right?
What I usually do, is to have a sql file like this:
DROP TABLE configutation_a;
DROP TABLE configutation_b;
CREATE TABLE configutation_a;
INSERT INTO configutation_a (...);
CREATE TABLE configutation_b;
INSERT INTO configutation_b (...);
CREATE TABLE IF NOT EXIST user_data (...);
This means that every time the app starts, I am updating with the configuration data I have at that time (that's is why we use http.get to get any configuration file from a remote repo in the future) and create user data only if user_data table is not there (hopefully initial start).
Conclusion: It's always a good practice, in my opinion, to trust a database product 100% and abstractly let it do any transaction that might give you some risk if you implemented your self in your code; since it gives a tool for that.For example, the keyword [if not exists], is always safer than implementing a table checker your self.
I hope that helps.
PS: In case you refer in create database procedure, SQLite, connects to a database file and it doesn't exist, it creates it. For someone comfortable in sqlite command line, when you type
sqlite3 /home/user/db/configuration.db will connect you with this db and if the file is not there, it will create it.
I'm trying to create a database with SQLite3 but each time I run sqlite3 test.db it just takes me onto a new line and no database is created. I assumed I had to add a table to the database as well so I created one and once done it just says Error: near "sqlite3": syntax error. So creating a table to complete the database creation was not the issue. I have searched all over the web and each resource is telling me to do the same thing I have been doing that only results in an error. If this is the same syntax all other online resources are using successfully, why is it constantly failing to create a database for me?
Here is a screenshot of the exact attempt:
You seem to have the order/placement of commands mixed up. From the folder containing SQLite on your system, you should create a database via sqlite3 somedb.db:
C:\path\to\sqlite>sqlite3 test.db;
sqlite> <-- prompt lets you know that you have connected
Once you have connected to that database, you don't need to specify it again for operations intended against that database. So, I expect the following CREATE TABLE statement to work:
sqlite> CREATE TABLE test.testtbl (
...> col1 text,
...> col2 text,
...> col3 text);
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 am running a SQLite database in memory and I am attempting to drop a table with the following command.
DROP TABLE 'testing' ;
But when I execute the SQL statement, I get this error
SQL logic error or missing database
Before I run the "Drop Table" query I check to make sure that the table exists in the database with this query. So I am pretty sure that the table exists and I have a connection to the database.
SELECT count(*) FROM sqlite_master WHERE type='table' and name='testing';
This database is loaded in to memory from a file database and after I attempt to drop this table the database is saved from memory to the file system. I can then use a third party SQLite utility to view the SQLite file and check to see if the "testing" exists, it does. Using the same 3rd party SQLite utility I am able to run the "Drop TABLE" SQL statement with out error.
I am able to create/update tables without any problems.
My questions:
Is there a difference between a memory database and a file database in SQLite when dropping a table?
Is there a way to disable the ability to drop a table in SQLite that I may have accentually turned on somehow?
Edit: It appears to have something to do with a locked table. Still investigating.
You should not have quotes in your DROP TABLE command. Use this instead:
DROP TABLE testing
I had the same problem when using Sqlite with the xerial jbdc driver in the version 3.7.2. and JRE7
I first listed all the tables with the select command as follows:
SELECT name FROM sqlite_master WHERE type='table'
And then tried to delete a table like this:
DROP TABLE IF EXISTS TableName
I was working on a database stored on the file system and so it seems not to effect the outcome.
I used the IF EXISTS command to avoid listing all the table from the master table first, but I needed the complete table list anyway.
For me the solution was simply to change the order of the SELECT and DROP.
I want a debug function to do this, but I'm unaware of whether one already exists. Going through and using 'drop table' for each of my tables will be a pain.
Help appreciated.
Since the database is just one file, you can indeed just erase it. If you want something more automatic, you can use the following to do it all programmatically:
Recover your schema:
SELECT group_concat(sql,';') FROM sqlite_master;
Disconnect from the database
Delete the database file
Create your schema again with what was returned from the above query
If you used any particular options for your original database (page_size, etc), they will have to be declared manually as well.
to "drop database" for sqlite, simply delete the database file (and recreate if needed)