INTRODUCTION AND RELEVANT INFORMATION:
I have MS ACCESS 2007 database that I edit using ADO and C++.
PROBLEM:
My problem is that primary key also represents an ordinal number of the record, and after deletion, it should be properly updated. Primary key is of autonumber type.
Here is an example of what I am talking about:
| #PK | Other data ... |
| 1 | ... |
| 2 | ... |
| 3 | ... |
| 4 | ... |
| 5 | ... |
Now if I delete the 3rd record I get the following problem:
| #PK | Other data ... |
| 1 | ... |
| 2 | ... |
| 4 | ... |
| 5 | ... |
but I should get the following result:
| #PK | Other data ... |
| 1 | ... |
| 2 | ... |
| 3 | ... | // edited to reflect the change ( previous value was 4 )
| 4 | ... | // edited to reflect the change ( previous value was 5 )
If I delete last record and then insert new one I get this result:
| #PK | Other data ... |
| 1 | ... |
| 2 | ... |
| 3 | ... |
| 4 | ... |
| 6 | ... | // this should be 5
QUESTIONS:
Is there a way for me to programmatically update the autonumber field after I perform the DELETE query ?
EDIT:
Since I am aware this is a bad practice, I would prefer adding new field that should be ordinal number so my table can look like this:
| #PK | Ordinal | Other data ... |
| 1 | 1 | ... |
| 2 | 2 | ... |
| 4 | 3 | ... |
| 5 | 4 | ... |
but I would prefer it to update itself automatically. If this is not possible, I would prefer to update the field with SQL query after I perform the deletion.
Thank you.
Best regards.
It is possible, but not the right way. Primary keys are used for relationships, so if you change the values, you need to update all related tables. Even if you currently don't have any related tables, you still should consider adding a separate field for the order, otherwise you may face the same problem in the future when you want to add related tables.
EDIT To answer your question:
Is there a way to add another field that would represent ordinal number and will automatically increment after inserting new record?
If you set it to autonumber, it will automatically increment, but you will not be able to modify it. You can set it to number and when you insert, you use SELECT MAX(oredinal) + 1 FROM mytable to increment it.
For MS Access use
ALter Table Customer alter column CustomerID Counter(1,1)
For Sql Server
DBCC CHECKIDENT (orders, RESEED, 0)
This will set the value of the next ID to be 1, you can use above command.
Ref URL# http://www.howtogeek.com/howto/database/reset-identity-column-value-in-sql-server/
I have decided to add a new field in my table that will hold the ordinal number of the record.
If we assume the field is named OrdinalNumber then the following solution worked for me:
// when inserting record, I just had to add COUNT( PK ) + 1
INSERT INTO MyTable ( OrdinalNumber , ... ) SELECT COUNT( PK ) + 1 , ...
from MyTable ;
// when deleting, I had to perform following two queries :
DELETE from MyTable where PK = ? ;
// decrement all the successors ordinal number by one
UPDATE MyTable set OrdinalNumber = ( OrdinalNumber - 1 ) where ( PK > ? );
Everything seem to work well. I wish there was an easier way though...
Thanks everyone for helping. I have upvoted all the answers.
Related
I have 2 tables in powerbi, one contains all transactions to and from people (each client identified with an id, where "I" can be either the receiver or sender of $) and the other is the detail for each client.
Table 1 would look something like
| $ | sender id | receiver id |
|---|-----------| ------------|
| 10| 1 | 2 |
| 15| 1 | 3 |
| 20| 1 | 2 |
| 15| 3 | 1 |
| 10| 3 | 1 |
| 25| 2 | 1 |
| 10| 1 | 2 |
The second table contains sender id and name:
| id | name |
|----|-------|
| 1 | "me" |
| 2 | John |
| 3 | Susan |
The expected result is something like (not necesarily in a table, just to show)
| $ sent | $ received | Balance|
|--------|------------|--------|
| 55 | 45 | +10 |
And in a filter have "John" and "Susan" so when i Select one of them i could see $ sent, $received and balance for each of them.
The problem of course is that i end up with one active and one inactive relationship so if i apply such a filter i end up with 0 in sender/receiver and the whole value in the other (depending which is made active and inactive) and if i make another table that's "id sender"+"name sender" then i cant filter all at once.
Is it possible to do this?
I hope this is kinda understandable
You will need to add 2 columns to your user table
received = CALCULATE(SUM(T1[$]), Filter(T1, UserTable[id] = T1[reveicer id]))
The same you can do for send. Now in your visual, use the new columns.
Enjoy!
after going around a bit I found a way to solve this, probably not the most orthodox way to do it, but it works.
What I did is to add 2 columns to my sales table, one was labeled "movement" and in sql it is just a 'case' where when the receiver is 'me' its "Charged" and when the receiver is 'not-me' its "Payment", then i added a column with a case so it would always bring me the 'not-me' id, and i used that for may relationship with my users table.
Then I just added filters in my cards making one a "Payment" card and the other a "Charged" card.
This is all following the previous example, it was actually just a bit more tricky as I could actually have a payment from me to myself, but thats just another "case" for when it was 'me-me'
Hope this is understandable, english is not my first language and the information i actually used is partially confidential so i had to make the above example.
thanks all and have a nice day.
I have the following tables:
Table A:
___________________
| ID | NUMBER |
|__________|________|
| 10000378 | 1 |
| | |
Table B:
_________________________________________________
| ... | ID | Column 1 | Column 2 |
|____________|__________|____________|____________|
| ... | 10000378 | 7 | 2 |
| | | | |
Table A and Table B share the same ID value.
Not that it matters too much, the ID in Table A is it's key, and can be found in Table B.
Table A's NUMBER column tells me which Table B column to read.
For example:
IF
[Table A].[NUMBER] = 1
THEN
put the value of [Table B].[Column 1] into [Table B].[My Column]
... and so on
As a visual example (my desired result):
_______________________________________________________________
| ... | ID | Column 1 | Column 2 | My Column |
|____________|__________|____________|____________|_____________|
| ... | 10000378 | 7 | 2 | 7 |
| | | | | |
With My Column being the result I am after (which comes from Column 1 - as specified by Table A's NUMBER value for the ID of 10000378).
What I have tried so far
I have set up a 1-to-1 relationship between Table A and Table B (on the ID column`).
I then went into the Power Query Editor tried adding a Conditional Column:
But that doesn't allow me to reference Table A in any way.
So I decided to try the Append Queries as New option:
Selecting the Two tables radio button, setting Primary Table to Table B and Table to append to the primary table to Table B.
With the idea of creating the following structure from which I can get my desired result (but adding the NUMBER column, which I don't really want but can live with):
_____________________________________________________________________________
| ... | ID | Column 1 | Column 2 | NUMBER | My Column |
|____________|__________|____________|____________|_____________|_____________|
| ... | 10000378 | 7 | 2 | 1 | 7 |
| | | | | | |
Doing the append copied all of the contents of Table B and inserted the NUMBER column which is fine, but all the values in that NUMBER column are now null.
I don't understand why this is the case.
How can I achieve my desired result?
Appending queries is used when you have additional rows of data that you’d like to add to an existing query (i.e. union/union all in SQL). Joining tables in Power BI is called "merging":
You can find more details in Combine queries section of Tutorial: Shape and combine data in Power BI Desktop article.
Note that if you have a proper relationship defined between your tables in the model (also described in the article above).
To do this, first merge Table B with Table A and expand the columns you'd like to add to the table (Column 1 and Column 2).
Once you have that, then write your custom column, My Column:
if [NUMBER] = 1 then [Column 1]
else if [NUMBER] = 2 then [Column 2]
else <whatever you want to return if not 1 or 2>
I have a table (short version ofcourse) like the following
--------------------------------------------------------
|id | Simulation_Name | Simulation_Version | sim_key |
--------------------------------------------------------
| 1 | MySim1 | 1 | 10 |
| 2 | MySim1 | 2 | 10 |
| 3 | MySim2 | 1 | 11 |
| 4 | MySim2 | 2 | 11 |
--------------------------------------------------------
On the Front End, I just want to display the latest version for each simulation. I'd appreciate any help on how to do this using Django ORM. I know there is a Max field but that only works with dates..
Currently, I'm using Raw SQL with an inner join to achieve this.
Any pointers on ORM? Thanks in advance
This is how I do it right now,
SELECT *
FROM
simulation_table AS A INNER JOIN
(SELECT id, max(simulation_version) as max_version
from
simulation_table
group by sim_key) AS B
ON
A.sim_key= B.sim_keyAND A.simulation_version= B.simulation_version
Max should work with integers:
from django.db.models import Max
simulations = Simulation.objects.values('name').annotate(max_version=Max('version'))
Situation
I have the following query in Postgres 9.5.
update warehouse_shelf
set package_count = counter.result
from (
select count(id) as result, shelf_id
from warehouse_package
group by shelf_id
) counter
where counter.shelf_id = warehouse_shelf.id;
These are my tables.
warehouse_shelf
+----+------+---------------+
| ID | NAME | PACKAGE_COUNT |
+----+------+---------------+
| 1 | S1 | 3 |
| 2 | S2 | 1 |
| 3 | S3 | 0 |
+----+------+---------------+
warehouse_package
+----+------+---------------+
| ID | NAME | SHELF_ID |
+----+------+---------------+
| 1 | P1 | 1 |
| 2 | P2 | 1 |
| 3 | P3 | 1 |
| 4 | P4 | 2 |
+----+------+---------------+
Question
How do I execute the query above whenever I make a change to an individual package (e.g. save, delete, create, update etc) via django model?
I want to execute using django queryset if possible and avoid executing it as raw query.
Considering you have models and their foreign key relations:
from django.db.models import Count
shelves = WhShelf.objects.all()
for shelf in shelves:
count = WhPackage.objects.filter(shelf_id=shelf.id).aggregate(Count('shelf'))
shelf.update(package_count=count[shelf__count'])
Alterantively, you can run a single query:
WhShelf.objects.annotate(package_count=WhPackage.objects.
filter(shelf_id=shelf.id).aggregate(Count('shelf'))['shelf__count'])
My question is similar to Django Advanced Filtering but I need another approach:
Abstract:
Tables: manufacturer, supplies
Manufacturers have multiple supplies (1 or 0 in "supply" table)
I have a HTML form with multiple (20+ checkboxes) which should limit the queryset with AND queries (so standard). The HTML checkbox names equal MySQL field names. My table looks like this:
mysql> explain supply;
+----------------------+------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------------+------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| manufacturer_id | int(11) | NO | MUL | NULL | |
| supply1 | tinyint(1) | NO | | NULL | |
| supply2 | tinyint(1) | NO | | NULL | |
| supply3 | tinyint(1) | NO | | NULL | |
| [...] | tinyint(1) | NO | | NULL | |
| supply20 | tinyint(1) | NO | | NULL | |
Now in pseudo SQL, I'd like to:
User selected checkboxes supply2 and supply14: SELECT * FROM supply WHERE supply2 = 1 AND supply14 = 1;
User selected checkboxes supply1, supply9 and supply18: SELECT * FROM supply WHERE supply1 = 1 AND supply9 = 1 AND supply18 = 1;
I'm pretty sure I need some QuerySet with kwargs, but I'm unable to construct the view for my needs (still learning Django).
I wonder if the data model here couldn't use some tweaking? You might want to have a supply table with twenty rows and an intermediate table connecting them (that is a ManytoMany(Supply) or something like that). Then you could just have a multi select field, rather than 20 check boxes (unless you really need them for some other reason).
If you need to add another supply, it's simply adding another row, rather than a schema migration.
supplies = Supply.objects.filter( supply1 = 1 )
And if you want to filter again:
supplies = supplies.filter(supply2 = 1)
The filter() method returns a QuerySet, so you can chain as many filter() calls as you like.