Sqlite将字符串转换为日期

问题描述 投票：35回答：8

我将日期存储为sqlite数据库中的字符串，如“28/11/2010”。我想将字符串转换为日期。

具体来说，我必须在两个日期之间转换大量的字符串日期。

在postgresql中，我使用to_date('30/11/2010','dd/MM/yyyy')，我怎么能用sqlite做同样的事情？

像这样的东西：

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')
string sqlite date date-format
8个回答
63
投票

作为Sqlite doesn't have a date type，您需要进行字符串比较才能实现此目的。要做到这一点你需要扭转顺序 - 例如从dd / MM / yyyy到yyyyMMdd，使用像

where substr(column,7)||substr(column,4,2)||substr(column,1,2) 
      between '20101101' and '20101130'
18
投票

保存日期为TEXT（20/10/2013 03:26）要进行查询并在日期之间选择记录？

更好的版本是：

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

2013年10月20日的substr给出了20131020日期格式DATE（20131021） - 这使得SQL使用日期并使用日期和时间函数。

要么

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');

这是一行

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');
10
投票

你应该研究的一件事是SQLite date and time functions，特别是如果你将不得不操纵很多日期。这是使用日期的理智方式，代价是更改内部格式（必须是ISO，即yyyy-MM-dd）。

3
投票

与脆弱的substr值相比，UDF方法是我的偏好。

#!/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()

这将给你这些结果：

[{'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'}]

SQLite相当于任何强大的东西，是你应该避免的substr和instr调用的纠结编织。

1
投票

这是针对fecha（TEXT）格式的日期YYYY-MM-dd HH：mm：ss例如我想要Ene-05-2014（2014-01-05）的所有记录：

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

我将日期存储为'DD-MON-YYYY格式（2016年6月10日），以下查询适用于我搜索2个日期之间的记录。

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');
1
投票

如果源日期格式不一致，则substr函数存在一些问题，例如：

2017年1月1日或1月11日或11/11/2017或1/1/17等

所以我使用临时表跟踪了不同的apporach。如果存在，此片段输出'YYYY-MM-DD'+时间。

请注意，此版本接受日/月/年格式。如果你想要月/日/年交换前两个变量DayPart和MonthPart。此外，两年的日期'44 -'99假定为1944-1999，而'00 -'43假定为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;
0
投票

我有一个数据库，其中日期以d F Y格式存储（2017年11月20日）并将其转换为机器可读日期（Y-m-d）我使用此方法将整个表格更新为正确的格式。

如果您只想查看内部的日期格式，请选择我如何格式化日期。

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 '__ ___ ____';
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