Parent (licenseID, countChilds)
Child (hostID, licenseID)
Trying to write an after insert/update/delete trigger that fires when adding a record to the child table. It needs to count child records linked to the parent and then insert this value into the parent.
But I keep getting the SQL statement is not valid.
So far I have this:
I am using MS Access 2010.
I am fairly sure you can get away with DCount, for example, this works for me:
But I would still recommend not doing this and just getting your counts from a query.
This seems to work, at least for After Insert:
The After Update Data Macro would be a bit more involved because it might have to update two [License] records (one for [Host].[licenseID] and another for [Old].[licenseID]), or perhaps none (if [Host].[licenseID] did not change).
Related
I have a scenarios where Table A has reference to Table B , Table B has a reference on Table C column ...etc.
To implement an update task in my project I ought to implement it in two phase logic
i.e. delete the row first and add the latest again.
But unfortunately , when I try to delete a row in table A it has reference which in turn has reference to other table and so on. Hence my logic of delete and add does not work in a proper way all the time. Even if it is deleted and added again , the sequence at which it is being added is last i.e. as a new record. Hence I am losing all the earlier references track in the same order as old one.
Hence I would like to delete a row from a table without effecting the references i.e. for time being it should allow to ignore reference , once i added it again i.e update record then i need to re-enforce/enable back the reference.
Is it possible to do in such a way ? or there any other logic works in similar fashion or replace the original intention ? could anyone please provide your expertise advice on this ?
How general logic of windows service pack works ? can any one elaborate on that? or share some info or doc or blog regarding the same?
Thank you so much.
Regards,
Shyam
What you want to do is a bad practice, I would rethink your design. It doesn't let you delete the parent record because there are child records. That is what the database ii supposed to and to try to circumvent it is a 100% guarantee of bad data.
If what you are trying to accomplish is to move the child records to a new parent, that can be done but you add the new record first and then make updates. It is best if you have some field to be able to define what old record it used to be associated with or a mapping table to use to make many changes. Then you would need to run updates for every child table. This kind of thing shoudl be a one time change, not a regular practice. It certainly shoudl virtually never happen from the application and shoudl only be done by a qualified databse developer.
If what you are trying to accomplish is to inactivate the parent so it can no longer be used for some purposes(such as creating new orders) and leave the details for reporting (wouldn't want to lose the finacials for old orders), then you should put an active flag on the table and use that to filter records instead. Often this means creating a view of only active records and pointing the code to the view insted of directly to the table.
I have created a table of Cards that so far contains 10 rows. if I execute:
delete from [Card] where cardnumber = 00010 //this card being held in the last row
I get the resulting message (1 row(s) affected), which I would expect works, however upon opening the table I find that the row is still there.
Next I used Edit Top 200 Rows in SSMS to select the row manually and delete it, upon which it is removed from the table, but when I execute, the row is back in the table.
Finally, I created a stored procedure that returns a success when executed, but the changes are still not being kept.
What is strange however, is that I have a CardAmount table with a relationship to the Card table that holds points per card, and the cards are being removed from CardAmount.
I have had a look at this question, but I don't think that was ever resolved.
First guess (which turned out to be correct) would be an instead of delete trigger that forgot to actually affect the table it's meant to be performing the delete for.
This is a common error, especially if you're implementing some far reaching form of cascade (and can't just use ON DELETE CASCADE on the foreign key constraint) where you have to use an INSTEAD OF trigger but then neglect to perform the DELETE on the underlying table.
I have two tables that both have an ID number which are linked together (AllUsers and AllProfiles). When the user presses a button, I want the AllUsers table to check for IDs it has that are not present in the AllProfiles table and delete them. I'm new to SQLCE and hacked this together. The problem is, it keeps deleting the entire table. Why?
DELETE FROM AllUsers
WHERE EXISTS
(SELECT ID
FROM AllUsers
WHERE (ID NOT IN
(SELECT ID
FROM AllProfiles)))
Also, is this an efficient way of bulk deleting thousands of records? I tried Linq's DeleteAllOnSubmit but it was too slow. I'm hoping since the above is comparing two tables directly, it should be efficient.
(I don't want to use cascading as I need control of each table individually)
EDIT - The SELECT statement correctly returns the missing IDs, so there's something wrong with the DELETE FROM AllUsers WHERE EXISTS part.
You're basically saying
delete from allusers
where TRUE -- this is pseudo, but you get the idea
Your original query deletes the whole table because the only condition is boolean... if that returns data then it'll delete all the data. If your exists clause does not return data it would not delete any data.
You want something like this (I'm not fluent with CE, but you should be able to make a minor modification if it doesn't 100% transport over to CE):
delete from allusers
where id not in
(
select id
from allprofiles
)
I am running a query that fetches data(records) form a linked table from another database.
The linked table is populated by users using a form remotely, like the web.
I created this piece of code that queries the data from the linked table into a new table, like this:
`INSERT INTO NEW_TBL(ENT_CUS_NUM, ENT_FIRST_NAME, ENT_LAST_NAME, ENT_ADDRESS1, ENT_CITY, ENT_STATE, ENT_ZIP, ENT_PHONE)
SELECT LINK_TBL.CUS_NUM, LINK_TBL.FIRST_NAME, LINK_TBL.LAST_NAME, LINK_TBL.ADDRESS1, LINK_TBL.CITY, LINK_TBL.STATE, LINK_TBL.ZIP, LINK_TBL.PHONE
FROM LINK_TBL`
Is it possible to modify this query so that it inserts new records from the link table if the record has not already been added, or update existent records
that have been modified? Example: Lets say a person changes their address, Can I update or bring over only their address without re-inserting their entire record because of an address change?
This is what confuses, I could write an update statement but modifying this querying so that it brings over new records or update records with changes is way over my head.
I would appreciate your input and help.
Guy
If you can designate a field as a unique key, you can use REPLACE INTO instead of INSERT INTO at least with mysql
I've manually created some data adapters – using the auto-generated ones is not viable due to version incompatibilities, for a dataset made of a number of tables with the usual mixture of PK, FK constraints. Most of its working pretty smoothly so far, but after modifying the adapters to use DB sequences for the PKs (instead of the temporary one assigned to the rows in the dataset) when updating the DB with new ‘added’ rows, I’ve been hitting problems.
I added the sequences into the insert statements and changed PK parameter to output parameters, so that it would update the dataset row and thus update all the child rows as well (with the UPDATE CASCADE rule). The problem is that the child rows, that, before the update had a row state of added, are changed to a state of modified (I don’t agree this should even be happening, surely an added row should stay as added even if it’s modified!). Thus when we get round to updating the child table with the child rows, it fails as its expecting rows with the added state.
What’s the cleanest way I could get around this problem? Potential solutions I can think of:
Turning off UPDATE CASCADE and updating each child row manually after, updating the parents PK and changing each row back to added, after modifying it.
Creating a copy of the all the added rows in all tables of the dataset before starting updates and then updating the main copy after each tables updates marking all the correct rows back to added.
Any better ideas?