I can do this using multiple commands in C# for the app I'm creating, but prefer a stored proc to eliminate issues with latency/locks, etc. (hopefully):
I have a table of 10 extensions (important fields):
SortOrder, Extension, IsUsed
First record will be set to IsUsed = true
When calling the stored proc, I need the IsUsed of the NEXT record in sort order to be set to true,the current record that is true set to false. When I hit the last record, rotate back to the first record.
Use Case: I need to rotate through a bank of usable numbers. Multiple people use the app, so cannot reuse. a number within the last 4 minutes (Bank of 10 will suffice, but we can extend if necessary). When the user requests a number, they get the next avail. I can build the table however needed, so any and all options to achieve use case are welcome.
I need to set the flag to true on the 1st record when stored proc is called. All other records should be false.
I have seen this, which is of interest, but doesn't quite answer:
Get "next" row from SQL Server database and flag it in single transaction
If all that you're using this for is to return a number to identify a session, I'd suggest scrapping the whole table idea and letting SQL Server do the work for you.
You can create a SEQUENCE object that will cycle and return the next value for you, without needing to write any code or maintain any tables.
CREATE SEQUENCE dbo.Extension
AS integer
START WITH 5
INCREMENT BY 5
MINVALUE 5
MAXVALUE 50
CYCLE;
This will return the number 5 the first time it's called, up to the number 50 on call number 10, and then start back over. You can adjust the numbers in the code to more or less do whatever you would like, though.
Get the next value like this:
SELECT NEXT VALUE FOR dbo.Extension;
And when/if you need to extend the range:
ALTER SEQUENCE dbo.Extension
MAXVALUE 100;
Play around with the idea on the Rextester demo.
Edit: In light of the comments above and below, I'd still stick with a SEQUENCE, I think.
Every time your code calls the table for an extension, use a query along the lines of this:
SELECT
Extension
FROM
ExtTable
WHERE
SortOrder = NEXT VALUE FOR dbo.Extension;
Functionally, this should do what you're after, again with no code to write or maintain.
Related
I have two Coldfusion templates (getdata.cfm and generate.cfm). The first template getdata.cfm will retrieve from a database with a query, in addition to other tasks. It will retrieve exactly 16 rows of data and each row will have 8 fields. Such as this:
<cfquery datasource="xyz name="lista">
SELECT n1,n2,n3,n4,n5,n6,n7,n8
FROM atable
WHERE product = "abc"
ORDER BY date DESC LIMIT 16
</cfquery>
The second template will generate some random numbers and compare them against these 16 rows. There is a Refresh button on the second template to regenerate the numbers. This is how I would like it to work.
However, right now the only way for it to work is having the database <cfquery> in the second template, generate.cfm That means every time I press Refresh, it will access the database, retrieve the same 16 rows every time, and generate the random numbers. This is not ideal. Because the 16 rows are the same, it makes no sense to retrieve them every time a new set of random numbers get generated. It would be best to get them once, in the first template and somehow pass them to the second template. The 16 sets of numbers will need to be displayed on the screen at all times. The matched and unmatched numbers need to be shown.
How can I pass the whole query result from the first template to the second one without having to pass the 16 records as 16 lists via the form as form fields? Is this even possible? Thanks in advance.
Generate a set of random numbers.
Compare those numbers against a static set of data.
Repeat.
Do you need to do the comparison in the application (CFML) code? Can you generate the set of random numbers and send them to the DB as part of the query in a single request? That way, you get the records from the DB that match your set of numbers and not all 16.
Then every refresh would send the new set of random numbers to the DB, returning only the relevant data.
Alternately, you can use cfquery with the cachedWithin attribute in order to store the results of the query into memory for a specific amount of time while refreshing your random set of numbers.
https://cfdocs.org/cfquery
Is there a way for me to know if the stream of rows has ended? That is, if the job is on the last row?
What im trying to do is for every 10 rows do something, my problem are the last rows, for example in 115 rows, the last 5 wont happen but i need them to.
There is no built-in functionality in Talend which tells you if you're on the last row. You can work around this using one of the following:
Get the row count beforehand. For instance, if you have a file, you
can use tFileRowCount to count the number of rows, then when you
process your file, you use a variable for your current row
number, and so you can tell if you've reached the last row. If your
data come from a database, you could either issue a query that
returns the total number of rows beforehand, or modify your main
query to return the total number of rows in an additional column and
use that (using ranking functions).
Do some processing after the subjob has ended: There may be situations
where you need a special processing for the last row, you can achieve
this by getting the last row processed by the previous subjob (which
you have already saved, for instance, by putting a tSetGlobalVar
after your target, when your subjob is done, your variable contains the last written value).
Edit
For your use case, what you could do is first store the result of the API call in memory using tHashOutput, then read it with a tHashInput in order to process it, and you'll know then how many rows you have retrieved using tHashOutput's global variable tHashOuput_X_NB_LINE.
I am trying to create an indexed view using the following code (so that I can publish it to replication it as a table):
CREATE VIEW lc.vw_dates
WITH SCHEMABINDING
AS
SELECT DATEADD(day, DATEDIFF(day, 0, GETDATE()), number) AS SettingDate
FROM lc.numbers
WHERE number<8
GO
CREATE UNIQUE CLUSTERED INDEX
idx_LCDates ON lc.vw_dates(SettingDate)
lc.numbers is simply a table with 1 column (number) which is incremented by row 1-100.
However, I keep getting the error:
Column 'SettingDate' in view 'lc.vw_dates' cannot be used in an index or statistics or as a partition key because it is non-deterministic.
I realize that GETDATE() is non-deterministic. But, is there a way to make this work?
I am using MS SQL 2012.
Edit: The hope was to be able to Convert GetDate() to make it deterministic (it seems like it should be when stripping off the time). If nobody knows of a method to do this, I will close this question and mark the suggestion to create a calendar table as correct.
The definition of a deterministic function (from MSDN) is:
Deterministic functions always return the same result any time they are called with a specific set of input values and given the same state of the database. Nondeterministic functions may return different results each time they are called with a specific set of input values even if the database state that they access remains the same.
Note that this definition does not involve any particular span of time over which the result must remain the same. It must be the same result always, for a given input.
Any function you can imagine that always returns the date at the point the function is called, will by definition, return a different result if you run it one day and then again the next day (regardless of the state of the database).
Therefore, it is impossible for a function that returns the current date to be deterministic.
The only possible interpretation of this question that could enable a deterministic function, is if you were happy to pass as input to the function some information about what day it is.
Something like:
select fn_myDeterministicGetDate('2015-11-25')
But I think that would defeat the point as far as you're concerned.
Well, my problem is that each time that I make an update of a row, this row goes to the last place in the table. It doesn't really matter where was placed before.
I've read in this post Postgresql: row number changes on update that rows in a relational table are not sorted. Then, why when I execute a select * from table; do I always get the same order?
Anyway, I don't want to start a discussion about that, just to know if is there any way to don't let update sentence place the row in the last place.
Edit for more info:
I don't really want to get all results at all. I have programmed 2 buttons in Java, next and previous and, being still a begginer, the only way that I had to get the next or the previous row was to use select * from table limit 1 and adding offset num++ or offset num-- depending of the button clicked. So, when I execute the update, I lose the initial order (insertion order).
Thanks.
You could make some space in your tables for updates. Change the fill factor from the default 100%, no space for updates left on a page, to something less to create space for updates.
From the manual (create table):
fillfactor (integer)
The fillfactor for a table is a percentage
between 10 and 100. 100 (complete packing) is the default. When a
smaller fillfactor is specified, INSERT operations pack table pages
only to the indicated percentage; the remaining space on each page is
reserved for updating rows on that page. This gives UPDATE a chance to
place the updated copy of a row on the same page as the original,
which is more efficient than placing it on a different page. For a
table whose entries are never updated, complete packing is the best
choice, but in heavily updated tables smaller fillfactors are
appropriate. This parameter cannot be set for TOAST tables.
But without an ORDER BY in your query, there is no guarantee that a result set will be sorted the way you expect it to be sorted. No fill factor can change that.
Tough problem I am working on here.
I have a table of CustomerIDs and CallDates. I want to measure whether there is a 'repeat call' within a certain period of time (up to 30 days).
I plan on creating a parameter called RepeatTime which is a range from 0 - 30 days, so the user can slide a scale to see the number/percentage of total repeats.
In Excel, I have this working. I sort CustomerID in order and then sort CallDate from earliest to latest. I then have formulas like:
=IF(AND(CurrentCustomerID = FutureCustomerID, FutureCallDate - CurrentCallDate <= RepeatTime), 1,0)
CurrentCustomerID = the current row, and the FutureCustomerID = the following row (so it is saying if the customer ID is the same).
FutureCallDate = the following row and the CurrentCallDate = the current row. It is subtracting the future call time from the first call time to measure the time in between.
The goal is to be able to see, dynamically, how many customers called in for a specific reason within maybe 4 hours or 1 day or 5 days, etc. All of the way up until 30 days (this is our actual metric but it is good to see the calls which are repeats within a shorter time frame so we can investigate).
I had a similar problem, see here for detailed version Array calculation in Tableau, maxif routine
In your case, that is basically the same thing as mine, so you could apply that solution, but I find it easier to understand the one I'm about to give, I would do:
1) Create a calculated field called RepeatTime:
DATEDIFF('day',MAX(CallDates),LOOKUP(MAX(CallDates),-1))
This will calculated how many days have passed since the last call to the current. You can add a IFNULL not to get Null values for the first entry.
2) Drag CustomersID, CallDates and RepeatTime to the worksheet (can be on the marks tab, don't need to be on rows or column).
3) Configure the table calculation of RepeatTIme, Compute using Advanced..., partitioning CustomersID, Adressing CallDates
Also Sort by Field CallDates, Maximum, Ascending.
This will guarantee the table calculation works properly
4) Now you have a base that you can use for what you need. You can either export it to csv or mdb and connect to it.
The best approach, actually, is to have this RepeatTime field calculated outside Tableau, on your database, so it's already there when you connect to it. But this is a way to use Tableau to do the calculation for you.
Unfortunately there's no direct way to do this directly with your database.