I'm trying to filter out and report records in a database that fall between a specified date range. I'm there are other threads here on how to do something similar, but my dates are stored as date timestamps (which is why I think the issue is arising)
My current query is as follows:
"SELECT * FROM JOURNAL WHERE Date_Time>'10/10/2013 00:00:00'"
(Note that journal is the name of the table I'm pulling the data from and date_time is the field in which the date is stored. I'm aware the query doesn't quite do what I want it to yet, but I was just testing out a simpler case at first.)
When I run this query (as part of an excel macro), excel reports that it can't find any records even though I know their are records past this date. Does anyone know how to do this properly?
Edit: I've got it, it was an issue unrelated to the query (something else in the macro) Thanks so much for the help (changing the date format worked)
have you tried other date format? like this:
"SELECT * FROM JOURNAL WHERE Date_Time>'2013-10-10:00:00:00'"
A simple between statement is what you need:
SELECT * FROM JOURNAL WHERE Date_Time between '10/10/2013 00:00:00' and '[otherdate]'
You need to run this to check for one important thing: If the server is running the BETWEEN as inclusive or not. If it's inclusive, both dates are included. If not, the range will begin either before or after one or both.
I've seen SQL servers that are the same in every respect actually treat this condition differently. So it's a good idea to check that.
Related
Long time listener, first time caller.
At work we have all of the date columns for most tables stored in as a simple "string" (varchar) formats. Such as yyyymmdd (eg. 20220625) or yyyymm (202206) etc.
Now for a lot of queries that are time based we need to compare to current date, or some fixed offset from current date.
Now two obvious versions that I know of to get current utc date into either of those formats are the following (for yyyymm as example):
SELECT LEFT(CONVERT(VARCHAR, GETUTCDATE(), 112), 6) ...
SELECT CONVERT(VARCHAR(6), GETUTCDATE(), 112) ...
I'm wondering if anyone knows of a better way, either both idiomatically or performance wise to convert those, and/or is there anything wrong with the second one to be worried about versus the first one in regards to either security/reliability etc? The second one definitely satisfies my code golf sensibilities, but not if it's at the expense of something I'm unaware of.
Also for some extra context the majority of our code runs in SQL Server or T-SQL, BUT we also need to attempt to be as platform agnostic as possible as there are customers on Oracle and/or Mysql.
Any insight/help would be highly appreciated.
There is no problem with either approach. Both work just fine. It is a matter of personal preference which to choose. The first looks more explicit, the second is shorter and thus easier to read maybe. As to performance: You want to get the current day or month only once in a query, so the call doesn't realy affect query runtime.
As to getting this platform agnostic is quite a different story. SQL dialects differ. Especially when it comes to date/time handling. You already notice that SQL Server's date functions are quite restricted. In Oracle and MySQL you would simple state the format you want (TO_CHAR(SYSDATE, 'YYYYMM') in Oracle and DATE_FORMAT(CURRENT_DATE, '%Y%m') in MySQL). But you also see that the function calls differ.
Now, you could write a user defined function GET_CURRENT_MONTH_FORMATTED for this which would return the string for the current month, e.g. '202206'. Then you'd have the different codes hidden in that function and the SQL queries would all look the same. The problem, though, is how to tell the DBMS that the function result is deterministic for a particular timestamp? If you run the query on December 31, 2022 at 23:50 and it runs until January 1, 2023 at 0:20, you want the DBMS to call this function only once for the query resulting in '202212' and not being called again, suddenly resulting in another string '202301'. I don't even know whether this is possible. I guess it is not.
I think you cannot write a query that does what you want and looks the same in all mentioned DBMS.
I have a bunch of data in my database and I want to filter out data that has been stored that for longer than a week. I'm using SQLServer and I found that I could use the 'DATEDIFF' function.
At the moment it works great and fast but I don't have a lot of records at the moment therefore anything runs quite smoothly.
After some research online I found out that the comparison of integers in databases is faster than the comparison of strings, I assume at this point that the comparison of datetimes (using the given function) is even slower at a major scale.
Let's say my database table content looks like this:
Currently I would filter out records that are older like a week like so:
SELECT * FROM onlineMainTable WHERE DATEDIFF(wk, Date, GETDATE()) > 1
I assume that this query would be quite slow if there were a thousand rows tin the table.
The status column represents a calculation status, I wondered if I would speed up the process if I were to look for a specific status instead of matching datetimes, for me in order to set that status to the one that represents 'old records' I need to update those rows before I select them, it would look something like this:
UPDATE table SET Status = -1 WHERE NOT Status = -1 AND DATEDIFF(wk, Date, GETDATE()) > 1;
SELECT * FROM table WHERE Status = -1;
I used the '-1' as an example.
So obviously I could be wrong but I think updating in this case would be fast enough since there won't be that many records to update since older ones have already been updated with its status. The selection would be faster aswell since I would be matching integers instead of datetimes.
The downside to my (possible) solution is that I would query twice every time I fetch data, even when it might not be needed (if every row is newer than 1 week).
It comes down to this: Should I compare datetimes or should I update an integer column based on that datetime and then select using the comparison of those ints?
If there is a different/better way of doing this i'm all ears.
Context
I am making a webapp for quotation requests. Requests should expire after a week since they won't be valid at that point. I need to both display valid requests and expired requests (so costumers have an overview). All these requests are stored in a database table.
Indexes are the objects that are design to improve select queries performances the drawback is that they slow down insert delete and update operations, so they have to be used when necessary. Generally DBMS provide tools to explain queries execution plan.
Maybe you just need to add an index on Date column:
create index "index_name" on onlineMainTable(Date)
and query could be
SELECT * FROM onlineMainTable WHERE Date > DATEADD(week,-1,GETDATE());
I don't have much experience so I apologize in advance for a potentially dumb question. I did not create these tables nor the queries that have been used in the past. With that said --
For the past several months I have been using a date conversion query that was given to me to update columns from an integer to a date. It used to work just fine and I swear everything is the same for my latest data extractions, but at some point the dates started getting wonky. For example, a typical date column might look like:
58222
58158
59076
58103
And the conversion query looks something like this:
IIf([D_posting]<>0,[D_posting]-18261,0)
And returns the above dates as:
05/27/2059
03/24/2059
09/27/2061
01/28/2059
Which obviously is wrong. The situation kind of reminds me of how I remember we generated random numbers in C++ (which was a long time ago), but for the life of me I can't figure out how to reverse engineer the correct subtraction factor without a reference point.
I also tried using the CDate() function instead, and it resulted in a bunch of future dates also, leading me to wonder if there's something else wrong. I work for a small physicians group so it might be something in the Electronic Health Records software, but I'd like suggestion on what I should check to make sure it's nothing that I've done.
You could create a query that uses the 'cdate' function (see below) to return the date. You can modify the code so that it subtracts the offset (maybe 18261?)
In the immediate window of VBA you can tinker with the following:
The 'cdate' will take a number and convert it to a date:
?cdate(41925)
10/13/2014
The 'cdbl' will take a date and convert to a number.
?CDbl(Date())
41926
In our app people have 1 or multiple projects. These projects have a start and an end date. People have a limited amount of available days.
Now we have a page that displays the availability of a given person on a week by week basis. It currently shows 18 weeks.
The way we currently calculate the available time for a given week is like this:
def days_available(query_date=Date.today)
days_engaged = projects.current.where("start_date < ? AND finish_date > ?", query_date, query_date).sum(:days_on_project)
available = days_total - hours_engaged
end
This means that to display the page descibed above the app will fire 18(!) queries into the database. We have pages that lists the availability of multiple people in a table. For these pages the amount of queries is quickly becomes staggering.
It is also quite slow.
How could we handle the availability retrieval in a more performant manner?
This is quite a common scenario when working with date ranges in an entity. Easy and fastest way is in SQL:
Join your events to a number generated date table (see generate days from date range) so that you have a row for each day a person or people are occupied. Once you have the data in this form it is simply a matter of grouping by the week date part of the date and counting the rows per grouping.
You can extend this to group by person for multiple person queries.
From a SQL point of view, I'd advise using a stored procedure and pass in your date/range requirement, you can then return a recordset for a user or possibly multiple users. This way your code just has to access db once.
You can then output recordset data in one go, by iterating through.
Hope this helps.
USE Stored procedure to fire your query to SQL to get data.
Pass paramerts in your case it is today's date to the SQl query.
Apply your conditions and Logic in the SQL Stored procedure , Using procedure is the goood and fastest way to retrieve data from the SQL , also it will prevent your code from the SQL injection too.
Call that SP from your Code as i dont know the Ruby on raisl I cant provide you steps about how to Call the Stored procedure from it.
After that the data fdetched as per you stored procedure will be available in Data table or something like that.
After getting the data you can perform all you need
Hope this helps
see what query is executed. further you may make comand explain to your query
explain select * from project where start_date < any_date and end_date> any_date2
you see the plan of query . Use this plan to optimized your query.
for example :
if you have index using field end_date replace a condition(end_date> any_date2 and start_date < any_date) . this step will using index if you have index on this field. But it step is db dependent . example is for nysql. if you want use index in mysql you must have using index condition on left part of where
There's not really enough information in your question to know exactly what you're trying to achieve here, e.g. the code snippet doesn't make use of the returned database query, so you could just remove it to make it faster. Perhaps this is just a bug in the code you posted?
Having said that, there are some techniques you should look into to implement your functionality.
I would take a look at using data warehouse techniques. I would think of your 'availability information' as a Fact table in a star schema, with 'Dates' and 'People' as Dimension tables.
You can then use queries to get stuff like - list of users for this projects for this week, and their availability.
Data warehousing has a whole bunch of resources you can tap into to help make this perform well, but there's also a lot of terminology that can be confusing, but for this type of 'I need to slice and dice my data across several sets of things (people and time)', Data Warehousing techniques can be quite powerful.
As I dont understand ruby on rails,from sql point of view i suggest you to write a stored procedure and return a dataset.And do the necessary table operations on the dataset from front end.It will reduce the unnecessary calls to DB.
We have date columns in our database that are just a day - like birth date. However, SQL Server stores them as a date & time and the time in the records has various values (no idea how it ended up that way).
The problem is people will run a query for all birthdates <= {some date} and the ones that are equal aren't returned because a DateTime (using ADO.NET) set to a given date has a time of midnight.
I understand what's going on. The question is how best to handle this. We could force in a time of 23:23:59.999999999 to the date but that feels like it would have problems.
What's the standard best practice for handling this?
Simply add 1 day to {some_date} and use a less than comparison. Just make sure it's the next day at 12am...
If you need to query this frequently, I would probably add a computed, persisted column that casts your DATETIME to just a DATE (assuming you're on SQL Server 2008 or newer):
ALTER TABLE dbo.YourTableName
ADD JustDay AS CAST(YourDateTimeColumn AS DATE) PERSISTED
That way, you can now query on JustDay and it's just a DATE - no time portion involved. Since it's computed, there's no need to update it constantly; SQL Server will do this automagically for you. And since it's persisted, it's part of the table's on-disk structure and just as fast as a query on any other column - and it can even be indexed, if needed.
It's a classic space - vs - speed tradeoff - since you're now storing the date-only portion of all your birthdays, too, you're on-disk structure will be larger; on the other hand, since you have a nice, date-only column that can be indexed, you have a great way to speed up searches.
You say
The problem is people will run a query for all birthdates <= {some
date}
You could leave it as is and make sure people get rid of the time by using something like the following in their WHERE clauses:
CONVERT(DATETIME,CONVERT(CHAR(8),birthdates,112))<= {some date}
..or in later versions of SQL-Server:
CONVERT(DATE,birthdates)<= {some date}
But this is a workaround and best to take the other advice and get rid of the time in the actual target data.
One more option is:
DATEDIFF(d, birthdates, {some date}) <= 0