Which data type do I choose in SQLite to store a string such as "001" in the database.
I've tried using Text but when I go to type in the string 001, it drops the 00 and only puts a 1.
I've even tried using "blob" data type but still no luck. They all drop the zeros before the digit.
Works ok for me:
sqlite> create table sotest
...> (
...> col1 varchar(20)
...> );
sqlite>
sqlite> select * from sotest;
sqlite>
sqlite> insert into sotest values ('001');
sqlite> select * from sotest;
001
sqlite>
Maybe you weren't quoting your strings? For example:
sqlite> insert into sotest values ('001');
sqlite> select * from sotest;
001
sqlite> insert into sotest values (001);
sqlite> select * from sotest;
001
1
sqlite>
Column type should set to varchar, not string, if type is string zero will be dropped automatically.
Related
I'm a first time user for SQLite. I'm using command line SQLite, version 3.20.1 2017-08-24 16:21:36 on a Mac
I start SQLite by specifying the db file via the command line:
sqlite3 ~/www/sqlite/statistics.db
I try to create a table but receive the error duplicate column name
Advice appreciated. In the transcript below, I first tested with a 1 column table.
sqlite> CREATE TABLE api_methods(
...> id INTEGER PRIMARY KEY
...> );
sqlite> SELECT name FROM sqlite_master WHERE type='table';
api_methods
sqlite> drop table api_methods;
sqlite> CREATE TABLE api_methods(
...> id INTEGER PRIMARY KEY,
...> action_name TEXT NOT NULL
...> );
Error: duplicate column name:
sqlite>
Problem solved when I deleted the leading spaces before the column names:
sqlite> CREATE TABLE api_methods(
...> id INTEGER PRIMARY KEY,
...> action_name TEXT NOT NULL
...> );
sqlite> SELECT name FROM sqlite_master WHERE type='table';
api_methods
sqlite> pragma table_info(api_methods);
0|id|INTEGER|0||1
1|action_name|TEXT|1||0
sqlite>
these both statements seem to make a difference, but I do not yet get why:
ALTER TABLE FOO ADD COLUMN DELETED BOOLEAN NOT NULL DEFAULT FALSE
seems to behave differently than:
ALTER TABLE FOO ADD COLUMN DELETED BOOLEAN NOT NULL DEFAULT 0
can anyone shed some light on this - I thought FALSE is 0 and TRUE is 1 - but this boolean seems to have >= 4 states:
➜ ~ sqlite3
SQLite version 3.8.7.4 2014-12-09 01:34:36
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database.
sqlite> CREATE TABLE FOO ( id INTEGER );sqlite> INSERT INTO FOO ( id ) VALUES (1);
sqlite> select * from FOO;
1
sqlite> ALTER TABLE FOO ADD COLUMN DELETED BOOLEAN NOT NULL DEFAULT FALSE;sqlite> select * from FOO;
1|FALSE
sqlite> ALTER TABLE FOO ADD COLUMN DELETED2 BOOLEAN NOT NULL DEFAULT 0;
sqlite> select * from FOO;
1|FALSE|0
sqlite> ALTER TABLE FOO ADD COLUMN DELETED3 BOOLEAN NOT NULL DEFAULT TRUE;
sqlite> select * from FOO;
1|FALSE|0|TRUE
sqlite> ALTER TABLE FOO ADD COLUMN DELETED4 BOOLEAN NOT NULL DEFAULT 1;
sqlite> select * from FOO;
1|FALSE|0|TRUE|1
sqlite> select * from FOO WHERE DELETED;
sqlite> select * from FOO WHERE DELETED2;
sqlite> select * from FOO WHERE DELETED3;
sqlite> select * from FOO WHERE DELETED4;
1|FALSE|0|TRUE|1
Why exactly SQLite allows these ALTER TABLE statements to run as shown I don't know but the missing piece of the puzzle here is that those FALSE and TRUE values will be stored as strings.
Try this in the SQLite command line tool:
CREATE TABLE test (id integer, xx boolean not null default TRUE);
INSERT INTO test (id) VALUES (1)
.dump
You'll get this output:
sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE test (id integer, xx boolean not null default TRUE);
INSERT INTO "test" VALUES(1,'TRUE');
COMMIT;
As you can see, the TRUE value there is stored as a string.
Now, let's try to query for the TRUE value:
SELECT * FROM test WHERE xx = TRUE
this gives this error message:
Error: no such column: TRUE
So in short, TRUE or FALSE are not magical constants in SQLite SQL syntax for the boolean values. Why the ALTER TABLE statements allow for them to be specified without quotes I don't know, there's probably a good reason.
Here's the example from my comment:
ALTER TABLE test ADD COLUMN xy INTEGER NOT NULL DEFAULT MONKEYDOODLE;
Output from .dump:
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE test (id integer, xx boolean not null default TRUE, xy INTEGER NOT
NULL DEFAULT MONKEYDOODLE);
INSERT INTO "test" VALUES(1,'TRUE','MONKEYDOODLE');
COMMIT;
One final piece of the puzzle is also that SQLite doesn't really prevent you from storing values of different data types in the same column.
From the documentation:
Any column in an SQLite version 3 database, except an INTEGER PRIMARY KEY column, may be used to store a value of any storage class.
You can see this in effect here:
CREATE TABLE test (id integer);
INSERT INTO test VALUES (1);
INSERT INTO test VALUES ('test');
INSERT INTO test VALUES (DATE());
INSERT INTO test VALUES (10.5);
This is the output from .dump:
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE test (id integer);
INSERT INTO "test" VALUES(1);
INSERT INTO "test" VALUES('test');
INSERT INTO "test" VALUES('2015-07-20');
INSERT INTO "test" VALUES(10.5);
COMMIT;
I insert some data into test table.
C:\> sqlite3 e:\\test.db
sqlite> create table test(code TEXT,content numeric);
sqlite> insert into test(code,content)values('x',3);
sqlite> insert into test(code,content)values('x',1.5);
sqlite> insert into test(code,content)values('x',1);
sqlite> insert into test(code,content)values('y',9);
sqlite> insert into test(code,content)values('y',3);
sqlite> insert into test(code,content)values('y',2);
sqlite> insert into test(code,content)values('y',12.3);
sqlite> insert into test(code,content)values('y',11.5);
how can i get the ordered output as the following ?
select * from test group by code order by content;can not get it.
select * from test order by content;neither.
x|1
x|1.5
x|3
y|2
y|3
y|9
y|11.5
y|12.3
You can sort by multiple criteria:
SELECT * FROM test ORDER BY code, content;
Can I create a database constraint on a TEXT column in SQLite disallowing the value of the column to be empty string ""?
I want to allow the column to be null, but disallow empty string.
Yes you can:
sqlite> create table foo (bar TEXT, CHECK(bar <> ''));
sqlite> insert into foo values (NULL);
sqlite> insert into foo values ('bla');
sqlite> insert into foo values ('');
Error: constraint failed
You can use a CHECK constraint (http://www.sqlite.org/lang_createtable.html):
SQLite version 3.5.9
Enter ".help" for instructions
sqlite> create table example(col, CHECK (col is null or length(col) > 0));
sqlite> insert into example values ('');
SQL error: constraint failed
sqlite> insert into example values (null);
sqlite> insert into example values ('sample');
sqlite> .nullvalue NULL
sqlite> select col from example;
NULL
sample
As far as i know doesn't exist a similar constraint in SQLite, but maybe you can workaround with a Trigger that on INSERT and/or UPDATE automatically change the string empty in NULL.
is there a cast in sqlite, I need this to work in a create table definition ...
....
mydatetime numeric not null DEFAULT (strftime('%Y%m%d%H%M','now', 'localtime')) );
thanks
sqlite> .headers on
sqlite> CREATE TABLE t1 (mydatetime int not null DEFAULT (strftime('%Y%m%d%H%M',
'now', 'localtime')), otherval TEXT);
sqlite>
sqlite> INSERT INTO t1 (otherval) VALUES ('qwe');
sqlite> SELECT * FROM t1;
mydatetime|otherval
201201231947|qwe