When creating a database table in jupyter, we specify restrictions on data types in the columns of the table, but for some reason we can still add other data types. For example, the st_gr column should contain only numbers, but nothing will stop us from adding a line (code below) Why? How to fix?
%%sql sqlite://
CREATE TABLE students(
st_id INTEGER PRIMARY KEY AUTOINCREMENT,
fname VARCHAR(15) NOT NULL,
lname VARCHAR(15) NOT NULL,
st_gr NUMERIC
)
%%sql sqlite://
INSERT INTO students (fname, lname, st_gr) VALUES('Barack', 'Obama', 'text not num')
SQLite uses dynamic type system. Declared column type only indicates the preferred value type, unless the table is strict.
If you are using sqlite version > 3.37.0, look into using STRICT tables.
If not, perhaps check constraints? software verification? a different database?
So i am trying to complete finance. Following is the .schema:
sqlite> .schema
CREATE TABLE users (id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, username TEXT NOT NULL, hash TEXT NOT NULL, cash NUMERIC NOT NULL DEFAULT 10000.00);
CREATE TABLE sqlite_sequence(name,seq);
CREATE TABLE history(
symbol TEXT, name TEXT, shares INTEGER, price NUMERIC, time DATETIME
);
CREATE UNIQUE INDEX username ON users (username);
When i try to add foriegn key to history table it always return error. Here is my code:
sqlite> ALTER TABLE history ADD COLUMN id INT;
sqlite> ALTER TABLE history ADD FOREIGN KEY(id) REFRENCES users(id);
Parse error: near "FOREIGN": syntax error
ALTER TABLE history ADD FOREIGN KEY(id) REFRENCES users(id);
^--- error here
I think based on what I see in the sqlite docs that the statement should be together with the ADD column:
ALTER TABLE history ADD COLUMN id INTEGER REFERENCES users(id);
But you please check me on this syntax! Another option is to take care of creating the constraint at the same time that you create the table.
CREATE TABLE history(
symbol TEXT,
name TEXT,
shares INTEGER,
price NUMERIC,
time DATETIME,
id INTEGER,
FOREIGN KEY (id)
REFERENCES users (id));
It might not be something you have realized (yet) but every database has its unique flavor of SQL, so despite there being a SQL standard there are often little differences in the syntax of SQL for specific db implementations. So you always have to beware of this when looking up commands for your sql db.
Further detail on Sqlite foreign key constraints can be found here:
https://www.sqlitetutorial.net/sqlite-foreign-key/
I have it a point that has really got me stuck and help is need
I have two tables
1) Jobs
2) JobNotes
Jobs is made up like the following
ID integer PRIMARY KEY,
Name nvarchar(100) COLLATE NOCASE
etc..
JobNotes is made up like the following
ID integer PRIMARY KEY,
JobID integer .
Notes nvarchar(100) COLLATE NOCASE
FOREIGN KEY ([JobID ]) REFERENCES Jobs,
When i insert a job into the database I need to insert the jobnote and set the JobID to be the id of the job just inserted previously.
Has anyone got examples or know of a method this can be accomplished using phonegap & sqlite.
Best Regards,
Lmac
After doing the insert I get the max id and then pass this into another function that updates the Foreign key.
Its not the most desired way but so far seems to work.
I have a bunch of SQLite db files, and I need to merge them into one big db files.
How can I do that?
Added
Based on this, I guess those three commands should merge two db into one.
attach './abc2.db' as toMerge;
insert into test select * from toMerge.test
detach database toMerge
The problem is the db has PRIMARY KEY field, and I got this message - "Error: PRIMARY KEY must be unique".
This is the test table for the db.
CREATE TABLE test (id integer PRIMARY KEY AUTOINCREMENT,value text,goody text)
I'm just thinking off my head here... (and probably after everybody else has moved on, too).
Mapping the primary key to "NULL" should yield the wanted result (no good if you use it as foreign key somewhere else, since the key probably exists, but has different contents)
attach './abc2.db' as toMerge;
insert into test select NULL, value, goody from toMerge.test;
detach database toMerge;
actual test:
sqlite> insert into test select * from toMerge.test;
Error: PRIMARY KEY must be unique
sqlite> insert into test select NULL, value, goody from toMerge.test;
sqlite> detach database toMerge;
I'm not 100% sure, but it seems that I should read all the elements and insert the element (except the PRIMARY KEY) one by one into the new data base.
Can I make a field AUTOINCREMENT after made a table? For example, if you create a table like this:
create table person(id integer primary key, name text);
Then later on realise it needs to auto increment. How do I fix it, ie in MySQL you can do:
alter table person modify column id integer auto_increment
Is table creation the only opportunity to make a column AUTOINCREMENT?
You can dump the content to a new table:
CREATE TABLE failed_banks_id (id integer primary key autoincrement, name text, city text, state text, zip integer, acquired_by text, close_date date, updated_date date);
INSERT INTO failed_banks_id(name, city, state, zip, acquired_by,close_date, updated_date)
SELECT name, city, state, zip, acquired_by,close_date, updated_date
FROM failed_banks;
And rename the table:
DROP TABLE failed_banks;
ALTER TABLE failed_banks_id RENAME TO failed_banks;
Background:
The new key will be unique over all
keys currently in the table, but it
might overlap with keys that have been
previously deleted from the table. To
create keys that are unique over the
lifetime of the table, add the
AUTOINCREMENT keyword to the INTEGER
PRIMARY KEY declaration.
http://www.sqlite.org/faq.html#q1
SQLite limitations:
SQLite supports a limited subset of
ALTER TABLE. The ALTER TABLE command
in SQLite allows the user to rename a
table or to add a new column to an
existing table. It is not possible to
rename a column, remove a column, or
add or remove constraints from a
table.
http://www.sqlite.org/lang_altertable.html
Hack seems to exist:
It appears that you can set
PRAGMA writable_schema=ON;
Then do a manual UPDATE of the
sqlite_master table to insert an "id
INTEGER PRIMARY KEY" into the SQL for
the table definition. I tried it and
it seems to work. But it is
dangerous. If you mess up, you
corrupt the database file.
http://www.mail-archive.com/sqlite-users#sqlite.org/msg26987.html
From the SQLite Faq
Short answer: A column declared INTEGER PRIMARY KEY will autoincrement
So when you create the table, declare the column as INTEGER PRIMARY KEY and the column will autoincrement with each new insert.
Or you use the SQL statment ALTER to change the column type to an INTEGER PRIMARY KEY after the fact, but if your creating the tables yourself, it's best to do it in the initial creation statement.
Simplest way — Just export and re-import
It is possible, and relatively easy. Export the database as an sql file. Alter the SQL file and re-import:
sqlite3 mydata.db .dump > /tmp/backup.sql
vi /tmp/backup.sql
mv mydata.db mydata.db.old
sqlite3 mydata.db
sqlite>.read /tmp/backup.sql
You can do it with SQLite Expert Personal 4:
1) Select the table and then go to "Design" tab > "Columns" tab.
2) Click "Add" and select the new column name, and type INTEGER and Not Null > Ok.
3) Go to "Primary Key" tab in "Desgin tab". Click "Add" and select the column you just created. Check the "Autoincrement" box.
4) Click "Apply" on the right bottom part of the window.
If you go back to the "Data" tab, you will see your new column with the autogenerated numbers in it.
While the Sqlite site gives you an example how to do it with a table with only a three fields, it gets nasty with one of 30 fields. Given you have a table called OldTable with many fields, the first of which is "ID" filled with integers.
Make a copy of your database for backup.
Using the command program dot commands,
.output Oldtable.txt
.dump Oldtable
Drop Table Oldtable;
Open Oldtable.txt in Microsoft Word or a grep like text editor. Find and Replace your Integer field elements with NULL.(You may need to adjust this to fit your fields). Edit the Create Table line so the field that was defined as Integer is now INTEGER PRIMARY KEY AUTOINCREMENT.
Save as NewTable.txt
Back in the command program dot
.read NewTable.txt
Done.
ID is now autoincrement.
Yes
Do you have phpmyadmin installed? I believe if you go to the 'structure' tab and look along the right columnn (where the field types are listed) - I think you can change a setting there to make it autoincrement. There is also a SQL query that will do the same thing.
You cannot alter columns on a SQLite table after it has been created. You also cannot alter a table to add an integer primary key to it.
You have to add the integer primary key when you create the table.
Yes, you can make a column which is autoincrement. Modify the table and add a column. Keep in mind that it is of type INTEGER Primary Key.
you can alter the table, altering the column definition
Simple Answer is as below,
CREATE TABLE [TEST] (
[ID] INTEGER PRIMARY KEY AUTOINCREMENT,
[NAME] VARCHAR(100));
and you are done.