Before Inserting
Id Priority
1 . 1
2 . 2
3 . 3
After Inserting Id: 4, Priority 2
Id Priority
1 . 1
4 . 2
2 . 3
3 . 4
fairly new to postgres, and i have a table with a column named priority. this column should have unique values, and if you attempt to give a row a priority that already exists, it would basically insert it with that priority, and decrement all the priorities that are <= by one to accommodate it.
is there a term for this sort of behavior? i know it will involve a column with unique values, but are there any model constraints i can introduce to enable this sort of behavior? or do i need to manually code an algorithm to do this and account for all edge cases.
I wouldn't store priority as it's own field. Create the table as ID, priority, Date_entered. Then use:
Select ID, rank() over (order by priority, date_entered) as priority
...
I suspect since the rank can change so frequently, calculating it on the fly like this would be preferential to attempting to store the rank and keep it updated.
edit:
There is a logical flaw to this that I can spot already...if record 4 was inserted as priority 2 (so the database contains 2 priority 2 records), there really wouldn't be an easy way to inject ID 5 between ID 4 and 2 without manipulating the date_entered field.
second edit:
Allowing the priority column to be decimal (priority 2 entered, then priority 2.5 entered, and so on), then using the rank() function to resolve that to an integer would get around that. There isn't a pretty answer here that I can find
Related
I will need your help to generate random records from the table tblFruit based on the field Type (without no duplication)
As per the above table.
There are 4 type of fruit number 1,2,3,4
I want to generate x records dynamically from the table tblFruit (e.g 7 records).
Let say I need to get 7 random record of fruit .
My result should contains fruit of the different types. However, we need to ensure that the result contains only 7 records.
i.e
2 records of type 1,
2 records of type 2,
2 records of type 3,
1 records of type 4
e.g
Note: If i want to generate 10 records (without no duplication),
then i will get 2 records of each type and the two remaining records randomly of any type.
Much grateful for your help.
I might suggest:
select top (7) f.*
from tblfruit f
order by row_number() over (partition by type order by newid());
This will actually produce a result with approximately the same number of rows of each type (well, off by 1), but that meets your needs.
What I am trying to do is fairly simple. I just want to add a row number to a query. Since this is in Access is a bit more difficult than other SQL, but under normal circumstances is still doable using solutions such as DCount or Select Count(*), example here: How to show row number in Access query like ROW_NUMBER in SQL or Access SQL how to make an increment in SELECT query
My Issue
My issue is I'm trying to add this counter to a multi-join query that orders by fields from numerous tables.
Troubleshooting
My code is a bit ridiculous (19 fields, seven of which are long expressions, from 9 different joined tables, and ordered by fields from 5 of those tables). To make things simple, I have an simplified example query below:
Example Query
SELECT DCount("*","Requests_T","[Requests_T].[RequestID]<=" & [Requests_T].[RequestID]) AS counter, Requests_T.RequestHardDeadline AS Deadline, Requests_T.RequestOverridePriority AS Priority, Requests_T.RequestUserGroup AS [User Group], Requests_T.RequestNbrUsers AS [Nbr of Users], Requests_T.RequestSubmissionDate AS [Submitted on], Requests_T.RequestID
FROM (((((((Requests_T
INNER JOIN ENUM_UserGroups_T ON ENUM_UserGroups_T.UserGroups = Requests_T.RequestUserGroup)
INNER JOIN ENUM_RequestNbrUsers_T ON ENUM_RequestNbrUsers_T.NbrUsers = Requests_T.RequestNbrUsers)
INNER JOIN ENUM_RequestPriority_T ON ENUM_RequestPriority_T.Priority = Requests_T.RequestOverridePriority)
ORDER BY Requests_T.RequestHardDeadline, ENUM_RequestPriority_T.DisplayOrder DESC , ENUM_UserGroups_T.DisplayOrder, ENUM_RequestNbrUsers_T.DisplayOrder DESC , Requests_T.RequestSubmissionDate;
If the code above is trying to select a field from a table not included, I apologize - just trust the field comes from somewhere (lol i.e. one of the other joins I excluded to simply the query). A great example of this is the .DisplayOrder fields used in the ORDER BY expression. These are fields from a table that simply determines the "priority" of an enum. Example: Requests_T.RequestOverridePriority displays to the user as an combobox option of "Low", "Med", "High". So in a table, I assign a numerical priority to these of "1", "2", and "3" to these options, respectively. Thus when ENUM_RequestPriority_T.DisplayOrder DESC is called in order by, all "High" priority requests will display above "Medium" and "Low". Same holds true for ENUM_UserGroups_T.DisplayOrder and ENUM_RequestNbrUsers_T.DisplayOrder.
I'd also prefer to NOT use DCOUNT due to efficiency, and rather do something like:
select count(*) from Requests_T where Requests_T.RequestID>=RequestID) as counter
Due to the "Order By" expression however, my 'counter' doesn't actually count my resulting rows sequentially since both of my examples are tied to the RequestID.
Example Results
Based on my actual query results, I've made an example result of the query above.
Counter Deadline Priority User_Group Nbr_of_Users Submitted_on RequestID
5 12/01/2016 High IT 2-4 01/01/2016 5
7 01/01/2017 Low IT 2-4 05/06/2016 8
10 Med IT 2-4 07/13/2016 11
15 Low IT 10+ 01/01/2016 16
8 Low IT 2-4 01/01/2016 9
2 Low IT 2-4 05/05/2016 2
The query is displaying my results in the proper order (those with the nearest deadline at the top, then those with the highest priority, then user group, then # of users, and finally, if all else is equal, it is sorted by submission date). However, my "Counter" values are completely wrong! The counter field should simply intriment +1 for each new row. Thus if displaying a single request on a form for a user, I could say
"You are number: Counter [associated to RequestID] in the
development queue."
Meanwhile my results:
Aren't sequential (notice the first four display sequentially, but then the final two rows don't)! Even though the final two rows are lower in priority than the records above them, they ended up with a lower Counter value simply because they had the lower RequestID.
They don't start at "1" and increment +1 for each new record.
Ideal Results
Thus my ideal result from above would be:
Counter Deadline Priority User_Group Nbr_of_Users Submitted_on RequestID
1 12/01/2016 High IT 2-4 01/01/2016 5
2 01/01/2017 Low IT 2-4 05/06/2016 8
3 Med IT 2-4 07/13/2016 11
4 Low IT 10+ 01/01/2016 16
5 Low IT 2-4 01/01/2016 9
6 Low IT 2-4 05/05/2016 2
I'm spoiled by PLSQL and other software where this would be automatic lol. This is driving me crazy! Any help would be greatly appreciated.
FYI - I'd prefer an SQL option over VBA if possible. VBA is very much welcomed and will definitely get an up vote and my huge thanks if it works, but I'd like to mark an SQL option as the answer.
Unfortuantely, MS Access doesn't have the very useful ROW_NUMBER() function like other clients do. So we are left to improvise.
Because your query is so complicated and MS Access does not support common table expressions, I recommend you follow a two step process. First, name that query you already wrote IntermediateQuery. Then, write a second query called FinalQuery that does the following:
SELECT i1.field_primarykey, i1.field2, ... , i1.field_x,
(SELECT field_primarykey FROM IntermediateQuery i2
WHERE t2.field_primarykey <= t1.field_primarykey) AS Counter
FROM IntermediateQuery i1
ORDER BY Counter
The unfortunate side effect of this is the more data your table returns, the longer it will take for the inline subquery to calculate. However, this is the only way you'll get your row numbers. It does depend on having a primary key in the table. In this particular case, it doesn't have to be an explicitly defined primary key, it just needs to be a field or combination of fields that is completely unique for each record.
I have a dataset, where somehow the next singular data is added on top of the previous data for one row, and that for every column, which means,
row with ID 1 is the original pure data, but row with e.g ID 10 has added the data from the previous 9 datasets on itself...
what I now want is to get the original pure data for every distinct item, which means for every ID, how can I substract all data from lets say ID, 10? I would have to substract those of the previous one, for ID 9 and so on...
I want to do this either in SQL Server or in Rapidminer, I am working with those tools, any idea?
here is a sample:
ID col1 col2 col3
1 12 2 3
2 15 5 5
3 20 8 8
so the real correct data for Item with ID 3 is not 20, 8, 8 it is (20-15),(8-5),(8-5) so its 5,3,3...
subtract the later from its previous for every item except the first..
1 12 2 3
Try it out with lag series operator, it will work for sure! To get this operator you should install the series extension from the RM marketplace.
What this operator does - he copies the selected attributes and pushes every row of the example set for one point, so row with ID 1 gets a copy with ID 2 etc (you can also specify the value for a lag). Afterwards you can substract one value from another with Generate Attributes.
I think lag() is the answer to your question:
select (case when id = 1 then col
else col - lag(col) over (order by id)
end)
However, sample data would clarify the question.
Within RapidMiner there is the Differentiate operator contained in the Series extension (which is not installed by default and needs to be downloaded from the RapidMiner Marketplace). This can be used to calculate differences between attributes in adjacent examples.
I have created a view in my SQL Server database which will give me number of columns.
One of the column heading is Priority and the values in this column are Low, Medium, High and Immediate.
When I execute this view, the result is returned perfectly like below. I want to change or assign values for these priorities. For example: instead of Low I should get 4, instead of Medium I should get 3, for High it should be 2 and for Immediate it should be 1.
What should I do to achieve this?
Ticket# Priority
123 Low
1254 Low
5478 Medium
4585 High
etc., etc.,
Use CASE:
Instead of Low I should get 4, instead of Medium I should get 3, for
High it should be 2 and for Immediate it should be 1
SELECT
[Ticket#],
[Priority] = CASE Priority
WHEN 'Low' THEN 4
WHEN 'Medium' THEN 3
WHEN 'High' THEN 2
WHEN 'Immediate' THEN 1
ELSE NULL
END
FROM table_name;
EDIT:
If you use dictionary table like in George Botros Solution you need to remember about:
1) Maintaining and storing dictionary table
2) Adding UNIUQE index to Priority.Name to avoid duplicates like:
Priority table
--------------------
Id | Name | Value
--------------------
1 | Low | 4
2 | Low | 4
...
3) Instead of INNER JOIN defensively you ought to use LEFT JOIN to get all results even if there is no corresponding value in dictionary table.
I have an alternative solution for your problem by creating a new Priority table (Id, Name, Value)
by joining to this table you will be able to select the value column
SELECT Ticket.*, Priority.Value
FROM Ticket INNER JOIN Priority
ON Priority.Name = Ticket.Priority
Note: although using the case keyword is the most straight forward solution for
this problem
this solution may be useful if you will need this priority value in many places at your system
I have a column in the sql server called "Ordinal" that is used to indicate the display order of the rows. It starts from 0 and skips 10 for the next row. so we have something like this:
Id Ordinal
1 0
2 20
3 10
It skips 10 because we wanted to be able to move item in between items (based on ordinal) without having to reassign ordinal number for the entire table.
As you can imagine eventually, Ordinal number will need to be reassign somehow for a move in between operation either on surrounding rows or for the entire table as the unused ordinal numbers between the target items are all used up.
Is there any algorithm that I can use to effectively reorder the ordinal number for the move operation taken in the consideration like long term maintainability of the table and minimizing update operations of the table?
You can re-number the sequences using a somewhat complicated UPDATE statement:
UPDATE u
SET u.sequence = 10 * (c.num_below-1)
FROM test u
JOIN (
SELECT t.id, count(*) AS num_below
FROM test t
JOIN test tr ON tr.sequence <= t.sequence
GROUP BY t.id
) c ON c.id=u.id
The idea is to obtain a count of items with the sequence lower than that of the current row, multiply the count by ten, and assign it as the new count.
The content of test before the UPDATE:
ID Sequence
__ ________
1 0
2 10
3 20
4 12
The content of test after the UPDATE:
ID Sequence
__ ________
1 0
2 30
3 10
4 20
Now the sequence numbers are evenly spread again, so you can continue inserting in the middle until you run out of new sequence numbers; then you can re-number again.
Demo.
These won't answer your question directly--I just thought I might suggest some other approaches:
One possibility--don't try to do it by hand. Have your software manage the numbers. If they need re-writing, just save them with new numbers.
a second--use a "Linked List" instead. In each record store the index of the next record you want displayed, then have your code load that directly into a linked list.
Yet another simple approach. Let's say you're inserting a new record with an ordinal equal x.
First, check if there's a row having ordinal value equal x. In case there's one, just update all the records having the ordinal value equal or bigger than x increasing them by y. Then, you are safe to insert a new record.
This way you're sure you'll not run update every time and of course, you'll keep the order.