I have a database that stores date and time in a single column for each entry as -
8/29/2012 6:09:45 AM - as an example. I am looking for a way to query just today's date all regardless of the time.
Currently I use criteria in a query Like "*9/29/2012*". The issue is that each day that the report is needed the date in the criteria needs to be updated, eliminating the possibility to automate the report.
Is there a way to just to query current date with out have to overhaul the target tables, or having to update the query criteria daily?
Dates are stored as numbers and the integer portion is the date, so you can say:
CInt(MyDate)=Cint(Date)
You can also say:
CDate(Format(MyDate, "yyyy/mm/dd")) = Date()
Or
DateSerial(Year(Mydate),Month(MyDate),Day(Mydate))=Date()
Or
MyDate>=Date And MyDate<Date+1
This final example will take advantage of indexes.
29/09/2012 00:00:00 is equal to Date()
29/09/2012 23:50:00 is greater than Date() but less than Date+1
Related
I am working on a SQLite Database which contains a column which stores value in format yyyy-MM-dd HH:mm:ss. Now I need to create a filter to select rows with filter as this datetime column.
Query:
Select * from tbl_locations where datetime >= '2013-09-11 00:00:00' and datetime <='2013-09-13 00:00:00'
Above query is returning null set despite containing values in this slot(which I verified using select statement without filter.)
Any suggestion how can i get the required data set?
Perhaps this excerpt from the SQLite documentation will help you:
1.2 Date and Time Datatype
SQLite does not have a storage class set aside for storing dates and/or times. Instead, the built-in Date And Time Functions of SQLite are capable of storing dates and times as TEXT, REAL, or INTEGER values:
TEXT as ISO8601 strings ("YYYY-MM-DD HH:MM:SS.SSS").
REAL as Julian day numbers, the number of days since noon in Greenwich on November 24, 4714 B.C. according to the proleptic Gregorian calendar.
INTEGER as Unix Time, the number of seconds since 1970-01-01 00:00:00 UTC.
Applications can chose to store dates and times in any of these formats and freely convert between formats using the built-in date and time functions.
The date and time functions that you can use in your SQL to build your query are documented at http://www.sqlite.org/lang_datefunc.html
Ok, I tested this out in MySQL but hopefully it will work. I had a table that used timestamps, and changed the column to be of type text. Then I tried the following SQL query and got the same results that I normally would (besides trailing decimals)
SELECT timestamp(stock_quote_timestamp)
FROM stock.stock_quote
WHERE stock_quote_timestamp < timestamp('2013-10-07 11:05:30')##high_date
AND stock_quote_timestamp > timestamp('2013-10-03 14:09:03');##low_date;
So basically, just convert your text statements to timestamps so that they compare correctly. Oh, and you'll also need to state what else you're SELECTing, or you could do a compound select statement: SELECT *, timestamp(stock_quote_timestamp)...
I am new to DynamoDB, and had a question how I can find all of the live entries in my DynamoDb table. Each entry in my table has a start and end date. I am confused on how I can query for the entries that the current date falls between the start and end date. Any ideas how I can do this?
I understand that I can only have a primary and range key. Is it possible to query for other columns in the entry?
Each entry looks like this:
id: xxxxxx
startDate: 123456 // Epoch time
endDate: 334243 // Epoch time
If you do not know the hashkey of your item(looks like 'id' in your case) then the only way to query DynamoDB is using a full table scan.
You can do a table scan using multiple conditions, but this is inefficient.
First you'll need to establish current epoch time. Then you can look to see if current epoch falls between your start and end epoch times. Most SQL variants have a BETWEEN(now, start, end) function. If not, then you'd look for now >= start AND now <= end. And yes, you can return any column in your query.
i want to get all entries from a SQLite table, which have the timestamp from the same month.
For example, the user can type in "July" and then i want to get all entries made in the 7. month.
The current "time"-column is a simple string and in the Format (DD.MM.YYYY HH:MM:SS)
Is there a way to do this with SQLite or will i need to use code in my program?
Assuming that your time strings have a fixed length, you could use a query like this:
SELECT * FROM MyTable WHERE time LIKE '__.07%';
However, you should always stored dates in one of the supported date/time formats so that you are able to use the built-int date/time functions.
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 application that writes temperature values to a MySQL table every second, It consists of the temperature and a datetime field.
I need to pull these values out of the table at specific intervals, every second, minute, hour etc.
So for example I will need to pull out values between 2 datetime fields and show the temperature at the hour for each of them.
One option I've considered is to create a temporary table that holds a list of the time intervals generated using MySQL INTERVAL and then joining that against the main table.
I'm just wondering if there's some time and date functions in MySQL that I'm overlooking that would make this easier?
Thanks.
You could use between for your date, and then a conditional WHERE clause using time() that looks at the structure of the timestamp. If it has 00:00 (for instance, 16:00:00) within it, take it, if not, leave it.
Example (untested):
SELECT temp, date
FROM temperatures
WHERE (date BETWEEN '2009/01/03 12:00:00' AND '2009/01/04 12:00:00')
AND (time(date) LIKE '%:00:00')
ORDER BY date ASC
LIMIT 10