as we all know that the correct format for date and time value in sqlite is :
2014-06-18 01:00:00
my question : is there any method to validate date and time value before insert / update on sqlite, maybe when creating table, to make sure date and time data is correct, thanks
To enforce that a value is in any of the supported formats, you could just check that some built-in date function is able to parse it:
CREATE TABLE MyTable(
MyDate CHECK (date(MyDate) IS NOT NULL),
[...]
);
Related
I'm new to the SQL world and im going crazy trying to figure out how to SELECT date from a datetime field in SQLITE.
Example: value <11/11/2005 14:56>, i just want to select <11/11/2005> for EVERY ROW.
I tried strftime(), date(), CAST() and other functions but the output its always NULL.
For example i tried querying SELECT strftime('%d/%m/%Y' , columnname) AS date FROM tablename;
OUTPUT: "NULL" in every row
Can someone help me understand what im doing wrong and how can i fix it? Thank you!!!
It always returns NULL because MM/DD/YYYY is not a valid sqlite date format. Treat the column as a string and use substr and instr to drop off the time portion. Something like (no guarantees, check the doc!)
SELECT substr(columname,0,instr(columnname,' '))
Re comment "how to order by the date in descending order"
This problem is a good argument (the best argument?) for storing the date in a sqlite date/time format. There is a strategy in this post for converting MM/DD/YYYY to YYYY-MM-DD (which sorts dates correctly).
If it's not too late, it would be advisable to change the date storage to a valid sqlite date format. strftime can be used to present the date as desired, and sorting will be accurate.
I simply want to show a date and its day of the week from a table.
The following works:
select "invDate", (select extract (dow from timestamp '2014-09-22'))
from "tblInvMaster"
But the moment I try to use the actual field like the example below, it doesn't work:
select "invDate", (select extract (dow from timestamp "invDate"))
from "tblInvMaster"
The above gives a syntax error where the field name starts in timestamp.
What is the correct method of getting this to work?
The syntax
TYPENAME 'VALUE'
e.g.
TIMESTAMP '2014-01-01'
is only valid in SQL for type literals.
If you want to cast a non-literal value you must use an explicit cast. Most likely you don't require a cast at all, and can just write:
extract(dow from "invDate")
as "invDate" should already be a timestamp or date. If it isn't, you'll need to CAST("invDate" AS timestamp).
I have a number of "DATETIME's" for the following form e.x.:
2014-01-15T19:30:00-0800
I am successfully inserting them into an sqlite table that I created with the following statement:
CREATE TABLE STUFF(id unique,date_time DATETIME)
When I query using the statement below I get all the dates I inserted back but not ordered.
SELECT * FROM STUFF ORDER BY DATETIME(date_time) DESC;
I'm guessing this is a formatting issue but I'm not sure. Can anyone spot what I'm doing wrong?
This is not a date format supported by SQLite;
a time zone indicator must have the form ±HH:MM:
> SELECT DATETIME('2014-01-15T19:30:00-0800');
> SELECT DATETIME('2014-01-15T19:30:00-08:00');
2014-01-16 03:30:00
I have a SQLite database where I store the dates as ticks. I am not using the default ISO8601 format. Let's say I have a table defined as follows:
CREATE TABLE TestDate (LastModifiedTime DATETIME)
Using SQL, I wish to insert the current date and time. If I execute any of the below statements, I end up getting the date and time stored as a string and not in ticks.
INSERT INTO TestDate (LastModifiedTime) VALUES(CURRENT_TIMESTAMP)
INSERT INTO TestDate (LastModifiedTime) VALUES(DateTime('now'))
I have looked at the SQLite documenation, but I do not seem to find any option to obtain the current timestamp in ticks.
I can of course define a parameter in C# and store the value as a System.DateTime. This does result in the datetime getting stored to the database in ticks.
What I would like to do is be able to insert and update the current timestamp directly from within the SQL statement. How would I do this?
Edit:
The reason I want the data stored as ticks in the database, is that the dates are stored in the same format as stored by the ADO.Net data provider, and so that when the data is also queried using the ADO.Net provider it is correctly retrieved as a System.DataTime .Net type.
This particular oddity of SQLite caused me much anguish.
Easy way - store and retrieve as regular timestamp
create table TestDate (
LastModifiedTime datetime
);
insert into TestDate (LastModifiedTime) values (datetime('now'));
select datetime(LastModifiedTime), strftime('%s.%f', LastModifiedTime) from TestDate;
Output: 2011-05-10 21:34:46|1305063286.46.000
Painful way - store and retrieve as a UNIX timestamp
You can use strftime to retrieve the value in ticks. Additionally, to store a UNIX timestamp (roughly equivalent to ticks), you can can surround the number of seconds in single-quotes.
insert into TestDate (LastModifiedTime) values ('1305061354');
SQLite will store this internally as some other value that is not a UNIX timestamp. On retrieval, you need to explicitly tell SQLite to retrieve it as a UNIX timestamp.
select datetime(LastModifiedTime, 'unixepoch') FROM TestDate;
To store the current date and time, use strftime('%s', 'now').
insert into TestDate (LastModifiedTime) VALUES (strftime('%s', 'now'));
Full example:
create table TestDate (
LastModifiedTime datetime
);
insert into TestDate (LastModifiedTime) values (strftime('%s', 'now'));
select datetime(LastModifiedTime, 'unixepoch') from TestDate;
When executed by sqlite3, this script with print:
2011-05-10 21:02:34 (or your current time)
After further study of the SQLite documentation and other information found on date number conversions, I have come up with the following formula, which appears to produce correct results:
INSERT INTO TestDate(LastModifiedTime)
VALUES(CAST((((JulianDay('now', 'localtime') - 2440587.5)*86400.0) + 62135596800) * 10000000 AS BIGINT))
Seems like a painful way to produce something that I would expect to be available as a built-in datetime format, especially that the database supports the storing of datetime values in ticks. Hopefully, this becomes useful for others too.
Update:
The above formula is not perfect when it comes to daylight savings. See section Caveats And Bugs in SQLite docs regarding local time calculation.
The following will return the number of milliseconds since the UNIX Epoch:
SELECT (strftime('%s', 'now') - strftime('%S', 'now') + strftime('%f', 'now')) * 1000 AS ticks
It works by grabbing the number of seconds since the Unix Epoch (%s), subtracting the number of seconds in the current time (%S), adding the number of seconds with decimal places (%f), and multiplying the result by 1000 to convert from seconds to milliseconds.
The subtraction and addition are to add precision to the value without skewing the result. As stated in the SQLite Documentation, all uses of 'now' within the same step will return the same value.
I have an sqlite database which currently holds an integer field called Year which currently only stores the year. In future versions I want to store a full date and time.
I updated my table to include a FullDate field using alter table.
> ALTER TABLE Files ADD COLUMN UploadDate DATETIME DEFAULT 0;
Next, I want to migrate all the existing year fields to the new field. So I'm looking for something like:
> UPDATE Files SET UploadDate = (DATETIME('%Y-%m-%d', Year, 1, 1));
Unfortunately this doesn't seem to work as the result is empty. I also tried the date and strftime functions but they either result in incorrect data or empty data.
What's the proper way to update a DATETIME field with existing data in the same table?
The DATE and DATETIME functions don't have a format parameter.
For more: http://sqlite.org/lang_datefunc.html
The main catch is that SQLite does not have any date or time types, so that you might as well populate your field with:
UPDATE Files SET UploadDate = Year || '-01-01';
And that will do the exact same thing. Dates are not stored as typed, but can be evaluated as such against the date and time functions.