[string] Sqlite convert string to date

I have date stored as string in an sqlite database like "28/11/2010". I want to convert the string to date.

Specifically I have to convert lots of string dates between two dates.

In postgresql, I use to_date('30/11/2010','dd/MM/yyyy'), how can I do the same thing with sqlite?

Something like this:

SELECT * FROM table
    WHERE   to_date(column,'dd/MM/yyyy')
    BETWEEN to_date('01/11/2010','dd/MM/yyyy')
    AND     to_date('30/11/2010','dd/MM/yyyy')

I am storing the date as 'DD-MON-YYYY format (10-Jun-2016) and below query works for me to search records between 2 dates.

select date, substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2),  case 
substr(date, 4,3) 
when 'Jan' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Jan' , '01')) 
when 'Feb' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Feb' , '02')) 
when 'Mar' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Mar' , '03')) 
when 'Apr' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Apr' , '04')) 
when 'May' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'May' , '05')) 
when 'Jun' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Jun' , '06')) 
when 'Jul' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Jul' , '07')) 
when 'Aug' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Aug' , '08')) 
when 'Sep' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Sep' , '09')) 
when 'Oct' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Oct' , '10')) 
when 'Nov' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Nov' , '11')) 
when 'Dec' then strftime('%s', replace(substr(date,8,11) || '-' || substr(date,4,4) || substr(date, 1,2), 'Dec' , '12')) 
else '0' end as srcDate from payment where srcDate >= strftime('%s', '2016-07-06') and srcDate <= strftime('%s', '2016-09-06');

Saved date as TEXT( 20/10/2013 03:26 ) To do query and to select records between dates?

Better version is:

SELECT TIMSTARTTIMEDATE 
FROM TIMER 
WHERE DATE(substr(TIMSTARTTIMEDATE,7,4)
||substr(TIMSTARTTIMEDATE,4,2)
||substr(TIMSTARTTIMEDATE,1,2)) 
BETWEEN DATE(20131020) AND DATE(20131021);

the substr from 20/10/2013 gives 20131020 date format DATE(20131021) - that makes SQL working with dates and using date and time functions.

OR

SELECT TIMSTARTTIMEDATE 
FROM TIMER 
WHERE DATE(substr(TIMSTARTTIMEDATE,7,4)
||'-'
||substr(TIMSTARTTIMEDATE,4,2)
||'-'
||substr(TIMSTARTTIMEDATE,1,2)) 
BETWEEN DATE('2013-10-20') AND DATE('2013-10-21');

and here is in one line

SELECT TIMSTARTTIMEDATE FROM TIMER WHERE DATE(substr(TIMSTARTTIMEDATE,7,4)||'-'||substr(TIMSTARTTIMEDATE,4,2)||'-'||substr(TIMSTARTTIMEDATE,1,2)) BETWEEN DATE('2013-10-20') AND DATE('2013-10-21');

The UDF approach is my preference compared to brittle substr values.

#!/usr/bin/env python3
import sqlite3
from dateutil import parser
from pprint import pprint


def date_parse(s):
    ''' Converts a string to a date '''
    try:
        t = parser.parse(s, parser.parserinfo(dayfirst=True))
        return t.strftime('%Y-%m-%d')
    except:
        return None


def dict_factory(cursor, row):
    ''' Helper for dict row results '''
    d = {}
    for idx, col in enumerate(cursor.description):
        d[col[0]] = row[idx]
    return d


def main():
    ''' Demonstrate UDF '''
    with sqlite3.connect(":memory:") as conn:
        conn.row_factory = dict_factory
        setup(conn)

        ##################################################
        # This is the code that matters. The rest is setup noise.
        conn.create_function("date_parse", 1, date_parse)
        cur = conn.cursor()
        cur.execute(''' select "date", date_parse("date") as parsed from _test order by 2; ''')
        pprint(cur.fetchall())
        ##################################################

def setup(conn):
    ''' Setup some values to parse '''
    cur = conn.cursor()

    # Make a table
    sql = '''
    create table _test (
        "id" integer primary key,
        "date" text
    );
    '''
    cur.execute(sql)

    # Fill the table
    dates = [
        '2/1/03', '03/2/04', '4/03/05', '05/04/06',
        '6/5/2007', '07/6/2008', '8/07/2009', '09/08/2010',
        '2-1-03', '03-2-04', '4-03-05', '05-04-06',
        '6-5-2007', '07-6-2008', '8-07-2009', '09-08-2010',
        '31/12/20', '31-12-2020',
        'BOMB!',
    ]
    params = [(x,) for x in dates]
    cur.executemany(''' insert into _test ("date") values(?); ''', params)


if __name__ == "__main__":
    main()

This will give you these results:

[{'date': 'BOMB!', 'parsed': None},
 {'date': '2/1/03', 'parsed': '2003-01-02'},
 {'date': '2-1-03', 'parsed': '2003-01-02'},
 {'date': '03/2/04', 'parsed': '2004-02-03'},
 {'date': '03-2-04', 'parsed': '2004-02-03'},
 {'date': '4/03/05', 'parsed': '2005-03-04'},
 {'date': '4-03-05', 'parsed': '2005-03-04'},
 {'date': '05/04/06', 'parsed': '2006-04-05'},
 {'date': '05-04-06', 'parsed': '2006-04-05'},
 {'date': '6/5/2007', 'parsed': '2007-05-06'},
 {'date': '6-5-2007', 'parsed': '2007-05-06'},
 {'date': '07/6/2008', 'parsed': '2008-06-07'},
 {'date': '07-6-2008', 'parsed': '2008-06-07'},
 {'date': '8/07/2009', 'parsed': '2009-07-08'},
 {'date': '8-07-2009', 'parsed': '2009-07-08'},
 {'date': '09/08/2010', 'parsed': '2010-08-09'},
 {'date': '09-08-2010', 'parsed': '2010-08-09'},
 {'date': '31/12/20', 'parsed': '2020-12-31'},
 {'date': '31-12-2020', 'parsed': '2020-12-31'}]

The SQLite equivalent of anything this robust is a tangled weave of substr and instr calls that you should avoid.

I have a database where dates are stored in d F Y format (20 Nov 2017) and to convert it to a machine readable date(Y-m-d) I use this method to update the entire table to a proper format.

If you only want the date formatting look at the inner select how I formatted the date.

update TABLENAME as realTABLE set created_at = (
select 
    -- Get Year
    substr(tmpTABLE.created_at ,-4, 4)
     || '-' ||
     -- Get Month
      substr(
           replace (replace (replace (replace (replace (replace (replace (replace (replace (replace (replace (replace (tmpReis.szAanmaakDatum
           , ' Dec ', '-12-') , ' Nov ', '-11-') , ' Oct ', '-10-') , ' Sep ', '-09-') , ' Aug ', '-08-') , ' Jul ', '-07-') , ' Jun ', '-06-') , ' May ', '-05-') , ' Apr ', '-04-') , ' Mar ', '-03-') , ' Feb ', '-02-') , ' Jan ', '-01-')
           -- Get it from the original space location + 1, then get the two numbers.
           ,instr(tmpTABLE.created_at, ' ')+1, 2)
     || '-' ||
     -- Get day, prepend with a zero if there's a zero lacking.
     substr('00' || tmpTABLE.created_at, -2, 2) as foo
from TABLENAME as tmpTABLE 
where tmpTABLE.id = realTABLE.id    
-- Check for valid matching formats. don't do those that already were converted.
) where created_at like '_ ___ ____' 
or created_at like '__ ___ ____';

This is for fecha(TEXT) format date YYYY-MM-dd HH:mm:ss for instance I want all the records of Ene-05-2014 (2014-01-05):

SELECT 
 fecha 
FROM 
 Mytable 
WHERE 
 DATE(substr(fecha ,1,4) ||substr(fecha ,6,2)||substr(fecha ,9,2))
BETWEEN 
 DATE(20140105) 
AND 
 DATE(20140105);

convert a string into date little issue think with indexing mmm 3,3 but works added a month on to the date string

SELECT substr('12Jan20',1,2) as dday,
date(substr('12Jan20',6,7) ||'00-' || case substr('12Jan20',3,3) when 'Jan' then '01'
when 'Feb' then '02'
when 'Mar' then '03'
when 'Apr' then '04'
when 'May' then '05' 
when 'Jun' then '06'
when 'Jul' then '07'
when 'Aug' then '08'
when 'Sep' then '09'
when 'Oct' then '10'
when 'Nov' then '11'
when 'Dec' then '12' end  || '-'||substr('12Jan20',1,2), '+1 month') as tt

If Source Date format isn't consistent there is some problem with substr function, e.g.:

1/1/2017 or 1/11/2017 or 11/11/2017 or 1/1/17 etc.

So I followed a different apporach using a temporary table. This snippet outputs 'YYYY-MM-DD' + time if exists.

Note that this version accepts Day/Month/Year format. If you want Month/Day/Year swap the first two variables DayPart and MonthPart. Also, two year dates '44-'99 assumes 1944-1999 whereas '00-'43 assumes 2000-2043.

 BEGIN;

    CREATE TEMP TABLE [DateconvertionTable] (Id TEXT PRIMARY KEY, OriginalDate  TEXT  , SepA  INTEGER,  DayPart TEXT,Rest1 TEXT, SepB  INTEGER,  MonthPart TEXT, Rest2 TEXT, SepC  INTEGER,  YearPart TEXT, Rest3 TEXT, NewDate TEXT);
    INSERT INTO [DateconvertionTable] (Id,OriginalDate)  SELECT SourceIdColumn, SourceDateColumn From  [SourceTable];

    --day Part (If day is first)

    UPDATE [DateconvertionTable] SET SepA=instr(OriginalDate ,'/');
    UPDATE [DateconvertionTable] SET DayPart=substr(OriginalDate,1,SepA-1) ;
    UPDATE [DateconvertionTable] SET Rest1=substr(OriginalDate,SepA+1);

    --Month Part (If Month is second)

    UPDATE [DateconvertionTable] SET SepB=instr(Rest1,'/');
    UPDATE [DateconvertionTable]  SET MonthPart=substr(Rest1, 1,SepB-1);
    UPDATE [DateconvertionTable] SET Rest2=substr(Rest1,SepB+1);

    --Year Part (3d)

    UPDATE [DateconvertionTable] SET SepC=instr(Rest2,' ');

           --Use Cases In case of time string included
    UPDATE [DateconvertionTable]  SET YearPart= CASE WHEN SepC=0 THEN Rest2 ELSE substr(Rest2,1,SepC-1)  END;

           --The Rest considered time
    UPDATE [DateconvertionTable]  SET Rest3= CASE WHEN SepC=0 THEN  '' ELSE substr(Rest2,SepC+1) END;

           -- Convert 1 digit day and month to 2 digit
    UPDATE [DateconvertionTable] SET DayPart=0||DayPart WHERE CAST(DayPart AS INTEGER)<10;
    UPDATE [DateconvertionTable] SET MonthPart=0||MonthPart WHERE CAST(MonthPart AS INTEGER)<10;

           --If there is a need to convert 2 digit year to 4 digit year, make some assumptions...
    UPDATE [DateconvertionTable] SET YearPart=19||YearPart WHERE CAST(YearPart AS INTEGER)>=44 AND CAST(YearPart AS INTEGER)<100;
    UPDATE [DateconvertionTable] SET YearPart=20||YearPart WHERE CAST(YearPart AS INTEGER)<44 AND CAST(YearPart AS INTEGER)<100;

    UPDATE [DateconvertionTable] SET NewDate = YearPart  || '-' || MonthPart || '-' || DayPart || ' ' || Rest3;  

    UPDATE [SourceTable] SET SourceDateColumn=(Select NewDate FROM DateconvertionTable WHERE [DateconvertionTable].id=SourceIdColumn);
    END;

One thing you should look into is the SQLite date and time functions, especially if you're going to have to manipulate a lot of dates. It's the sane way to use dates, at the cost of changing the internal format (has to be ISO, i.e. yyyy-MM-dd).