Data types

Remarks#

official documentation: Datatypes In SQLite Version 3

TYPEOF function

sqlite> SELECT TYPEOF(NULL);
null
sqlite> SELECT TYPEOF(42);
integer
sqlite> SELECT TYPEOF(3.141592653589793);
real
sqlite> SELECT TYPEOF('Hello, world!');
text
sqlite> SELECT TYPEOF(X'0123456789ABCDEF');
blob

Using booleans

For booleans, SQLite uses integers 0 and 1:

sqlite> SELECT 2 + 2 = 4;
1
sqlite> SELECT 'a' = 'b';
0
sqlite> SELECT typeof('a' = 'b');
integer

> CREATE TABLE Users ( Name, IsAdmin );
> INSERT INTO Users VALUES ('root', 1);
> INSERT INTO Users VALUES ('john', 0);
> SELECT Name FROM Users WHERE IsAdmin;
root

Enforcing column types

SQLite uses dynamic typing and ignores declared column types:

> CREATE TABLE Test (
      Col1 INTEGER,
      Col2 VARCHAR(2),       -- length is ignored, too
      Col3 BLOB,
      Col4,                  -- no type required
      Col5 FLUFFY BUNNIES    -- use whatever you want
  );
> INSERT INTO Test VALUES (1, 1, 1, 1, 1);
> INSERT INTO Test VALUES ('xxx', 'xxx', 'xxx', 'xxx', 'xxx');
> SELECT * FROM Test;
1   1   1   1   1         
xxx xxx xxx xxx xxx

(However, declared column types are used for type affinity.)

To enforce types, you have to add a constraint with the typeof() function:

CREATE TABLE Tab (
    Col1 TEXT   CHECK (typeof(Col1) = 'text' AND length(Col1) <= 10),
    [...]
);

(If such a column should be NULLable, you have to explicitly allow 'null'.)

Date/time types

SQLite has no separate data type for date or time values.

ISO8601 strings

The built-in keywords CURRENT_DATE, CURRENT_TIME, and CURRENT_TIMESTAMP return strings in ISO8601 format:

> SELECT CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP;
CURRENT_DATE  CURRENT_TIME  CURRENT_TIMESTAMP  
------------  ------------  -------------------
2016-07-08    12:34:56      2016-07-08 12:34:56

Such values are also understood by all built-in date/time functions:

> SELECT strftime('%Y', '2016-07-08');
2016

Julian day numbers

The built-in date/time functions interpret numbers as Julian days:

> SELECT datetime(2457578.02425926);
2016-07-08 12:34:56

The julianday() function converts any supported date/time value into a Julian day number:

> SELECT julianday('2016-07-08 12:34:56');
2457578.02425926

Unix timestamps

The built-in date/time functions can interpret numbers as Unix timestamps with the unixepoch modifier:

> SELECT datetime(0, 'unixepoch');
1970-01-01 00:00:00

The strftime() function can convert any supported date/time value into a Unix timestamp:

> SELECT strftime('%s', '2016-07-08 12:34:56');
1467981296

unsupported formats

It would be possible to store date/time values in any other format in the database, but the built-in date/time functions will not parse them, and return NULL:

> SELECT time('1:30:00');   -- not two digits

> SELECT datetime('8 Jul 2016');