Is there any difference between these two queries?
select * from tbl where ts < '9999-12-31-24.00.00.000000';
and
select * from tbl where ts < timestamp('9999-12-31-24.00.00.000000');
When is the timestamp function required?
Is there a difference in performance?
If ts is a string type:
1st one is comparing like for like as strings
2nd one will cause ts to be converted to date/time
If ts is a date/time type,
1st one will convert the constant to the same date time type as the ts column
2nd one is comparing like for like as date/time
If ts is string type, the 2nd one is worst to use because ts will be converted thus invalidating any indexes.
If ts is date/time, there is no difference
Data type precedence applies to most DB engines
At first glance, the first statement will make a string comparison while the second should make date related comparisons.
It depends on your SQL implementation, although assuming the column "ts" is some date/time type, there's practically no difference.
Most SQL implementations have a cast mapping that instructs the engine how to automatically convert data types that fit some pattern, especially if a literally comparison makes no sense. For example, literally comparing a timestamp to a string doesn't make much sense. However, most engines have a mapping that lets it know a string formatted like a date can be automatically converted to a timestamp, in order to be compared to another timestamps.
Related
I am not getting data between two years, below is between condition
to_char(Wfc.APPLYDTM,'MM/DD/YYYY') between '12/11/2019' and '01/10/2020'
but I am getting data between '12/11/2019' and '12/31/2019' & '01/11/2020' and '01/01/2020' for these dates but not between two different years.
Please help
Try using TO_DATE instead of TO_CHAR, and then compare against valid Oracle date literals:
SELECT *
FROM Wfc
WHERE TO_DATE(APPLYDTM, 'MM/DD/YYYY') BETWEEN date '2019-12-11' AND date '2019-01-10';
Note that if APPLYDTM already be a date, then you don't need to call TO_DATE on it. It doesn't make sense to convert your data to character, if you intend to work with it as a date.
You should convert your data to Date to be able to compare correctly.
The main idea is you should compare date value instead of string value.
to_date(Wfc.APPLYDTM,'MM/dd/yyyy') between to_date('12/11/2019','MM/dd/yyyy') and to_date('01/10/2020','MM/dd/yyyy')
Read here to more details.
Do not convert date/time values to strings! Use the built in functionality.
Your logic is most simply expressed as:
Wfc.APPLYDTMbetween >= DATE '2019-12-11' AND
Wfc.APPLYDTMbetween < DATE '2020-01-11'
Note that the date constants are provided using the DATE keyword. This supposed ISO 8601 standard date formats (happily!).
Also note the use of >= and < rather than BETWEEN. The date data type in Oracle can include a time component -- even if you don't see it when you query the table. This ensures that all date/times are included in the range.
As an added benefit, this can use an index on (APPLYDTMbetween). Using a function usually precludes using an index, unless you have defined a function-based index.
The Query using LIKE :(This query when fired gives the desired result)
select * from catissue_audit_event where event_timestamp like '16-DEC-14'
But when using query with '=' results in an empty resultset
select * from catissue_audit_event where event_timestamp='16-DEC-14'
Here event_timestamp is of type Date
Strange thing is that the query runs for other dates such as:
select * from catissue_audit_event where event_timestamp='15-DEC-14'
What can be the issue? I already checked for leading and trailing spaces in the data
Output after running the first query:
In Oracle a DATE (and of course a TIMESTAMP) column contains a time part as well.
Just because your SQL client is hiding the time, doesn't mean it isn't there.
If you want all rows from a specific day (ignoring the time) you need to use trunc()
select *
from catissue_audit_event
where trunc(event_timestamp) = DATE '2014-12-16';
Be aware that this query will not use an index on the event_timestamp column.
You should also not rely on implicit data type conversion as you do with the expression event_timestamp = '16-DEC-14. That statement is going to fail if I run it from my computer because of different NLS settings. Always use a proper DATE literal (as I have done in my statement). If you don't like the unambiguous ISO date, then use to_date():
where trunc(event_timestamp) = to_date('16-12-2014', 'dd-mm-yyyy');
You should avoid using month names unless you know that all environments (which includes computers and SQL clients) where your SQL statement is executed are using the same NLS settings. If you are sure, you can use e.g. to_date('16-DEC-14', 'dd-mon-yy')
The reason why this is different is different to the solution to your issue.
The solution to your issue is to stop performing date comparisons by implicit conversion to a string. Convert your string to a date to perform a date comparison:
select * from catissue_audit_event where event_timestamp = date '2014-12-16'
I cannot stress this enough; when performing a date comparison only compare dates.
Your column EVENT_TIMESTAMP is being implicitly (this is bad) converted to a date in accordance with your NLS_DATE_FORMAT, which you can find as follows:
select * from nls_session_parameters
This governs how date-data is displayed and implicitly converted. The reason why LIKE works and and = doesn't is because your NLS_DATE_FORMAT is masking additional data. In other words, your date has a time component.
If you run the following and then re-select the data from your table you'll see the additional time component
alter session set nls_date_format = 'yyyy-mm-dd hh24:mi:ss'
Thus, if you want all the data for a specific date without constraint on time you'll need to remove the time component:
select * from catissue_audit_event where trunc(event_timestamp) = date '2014-12-16'
have you tried matching the event_timestamp format example: DD-MMM-YY with the date that you are passing?
I am querying a SQLite database table as follows:
SELECT MAX(Date) from Intra360 WHERE Date <= "05/04/2013 00:00"
The right record in return should be the number 47, i.e. 04/04/2013 23:00:
However, the execution of this statement returns a different value:
I confess I know almost nothing about SQL, but this outcome is strange. Where am I being wrong?
NOTE "Intra360" is the name of the table and the field containing the dates is called "Date"
ADDITIONAL NOTE what I need is the closest available date to a user input. It is a Python program which is making some analysis but when the user inputs the dates is not necessarily true they will exist in the database. So I'm just trying to re-select them in a way that the proper SQL statement that will load the data to be used in the analysis won't fail execution because of the missing record. So "05/04/2013 00:00" is the user input, and the query should be done hence starting from 04/04/2013 (and not definetely 04/06/2013).
The comparisons are performed on strings with alphabetical ordering, not on datetime stamps with chronological ordering.
Store your datetimes in a format that compares the way you want. For example, unix epoch timestamps and ISO 8601 yyyy-MM-dd'T'HH:mm:ss datetimes have this property.
If you cannot influence how the data is stored, you can use substr() to mangle the timestamps in SQL. See e.g. Sqlite convert string to date for more.
i'm new to MS Access..
one of my Access table CHECKOUT having a column name CHECK-TIME with Date/time data type
values in that column are like 7/15/2013 10:56:22 AM,9/19/2013 6:54:37 PM....
i want to select the data based on date like `7/15/2013'
how to write the query for this task ???
thanks in advance..
First off, the way to specify date literals is with hash (#) not any form of quote or backtick.
Secondly, you can't do LIKE comparisons with dates, not that I've ever seen anyway.
Thirdly, it's always best to specify dates in yyyy-mm-dd format because it's an unambiguous format.
This example should give you what you need:
SELECT
*
FROM
CHECKOUT
WHERE
datevalue([CHECK-TIME]) = #2013-07-15#
The datevalue() function takes a parameter, usually a string but in this case a datetime, and converts it to a date, thus stripping off the time. This allows us to check for equality against a date literal.
I have a value in field called "postingdate" as string in 2009-11-25, 12:42AM IST format, in a table named "Post".
I need the query to fetch the details based on date range. I tried the following query, but it throws an error. Please guide me to fix this issue. Thanks in advance.
select postingdate
from post
where TO_DATE(postingDate,'YYYY-MM-DD')>61689
and TO_DATE(postingDate,'YYYY-MM-DD')<61691
As you've now seen, trying to perform any sort of query against a string column which represents a date is a problem. You've got a few options:
Convert the postingdate column to some sort of DATE or TIMESTAMP datatype. I think this is your best choice as it will make querying the table using this field faster, more flexible, and less error prone.
Leave postingdate as a string and use functions to convert it back to a date when doing comparisons. This will be a performance problem as most queries will turn into full table scans unless your database supports function-based indexes.
Leave postingdate as a string and compare it against other strings. Not a good choice as it's tough to come up with a way to do ranged queries this way, as I think you've found.
If it was me I'd convert the data. Good luck.
In SQL Server you can say
Select postingdate from post
where postingdate between '6/16/1969' and '6/16/1991'
If it's really a string, you're lucky that it's in YYYY-MM-DD format. You can sort and compare that format as a string, because the most significant numbers are on the left side. For example:
select *
from Posts
where StringDateCol between '2010-01-01' and '2010-01-02'
There's no need to convert the string to a date, comparing in this way is not affected by the , 12:42AM IST appendage. Unless, of course, your table contains dates from a different time zone :)
You will need to convert your string into a date before you run date range queries on it. You may get away with just using the string if your not interested in the time portion.
The actual functions will depend on your RDBMS
for strings only
select * from posts
where LEFT(postingDate,10) > '2010-01-21'
or
for datetime ( Sybase example)
select * from posts
where convert(DateTime,postingDate) between '2010-01-21' and '2010-01-31'