I have a typical Access front-end with SQL Server back-end. I created some views in SQL Server and linked to them in Access. When I use "CREATE INDEX index_name ON view_name (field_name)" it creates a primary key even though I have not specified it to do so (and do not want it to do so). Why is that? and how can I create a non-primary key index?
How this works?
Any view, any linked table, in fact ANYTHING you hit, use, consume from SQLServer?
All indexing is setup 100% in SQLServer. The Access client side does not, cannot, and WILL not create any kind of index for you.
The create index command to specify and setup a primary key? It does not really create an index in Access but ONLY SETS and TELLS Access what PK to use.
In fact, when you link to a view, you are prompted to select the PK when linking to a view.
SQLServer views DO NOT have the concept or even a setting that tells you or EVEN LETS you specify the PK column. Part of the reason for this is in fact that a view can consist of more than one table - so which table now is to define the primary key. And in fact if your view has a join with say 5 tables? Then in fact that view has 5 different primary keys from 5 different tables).
So, when you link to a view in access, you will note this prompt:
If you don't select a column for the pk?
Then you have no PK set. However, you can use VBA to TELL ACCESS what row to be the PK setting.
So, say in above I did not select a PK when linking with the GUI. Or say I am using code to link to a view?
Then in code to set the PK value, I would and could and should execute the following command:
CurrentDb.Execute "CREATE UNIQUE INDEX IXPK ON dbo_ViewHotelsTest (ID) WITH PRIMARY"
AGAIN: Note above comments. The create unique index DOES NOT create an index in Access. Nor does it create an index on SQLServer. That command is how you can tell Access which column is to be seen and treated as the PK.
So, above command?
In plain English:
Please Mr. Access, will you set the PK column and we are using the above
command to do this.
In other words, there is no other command in code to "tell" Access what the PK is supposed to be, so the DDL sql create index command is used. But I STRESS AGAIN THIS does NOT really create an index, but ONLY tell Access what column to use as the PK.
This command results in the SAME and IDENTICAL results if you select a PK during a linking of a view.
If you want to create an index in SQLServer? Then go to SQLServer, and create your index(es) in SQLServer.
FYI:
As a further explanation, in 99% of cases you NEVER want, nor need, or even should even create an index on a view on the SQLServer side of things.
In EVERY case, if the base table used for the source of the view has an index that can be used, it WILL IN ALL cases be used if you build an on-the-fly query, build a SQLServer side view, or even create a sql stored procedure. IN ALL cases, a simple create of an index on the base source table (using SQLServer tools) will suffice, and in ALL cases, include views, and including linked view from Access will automatic use ANY and ALL existing indexes on the base table from SQLServer.
So, not only is there zero requirements to EVER try and create an index in Access on linked tables (or linked views), but in fact it not even possible. Of course the create index command DOES need to be used to set the PK column when linking to a view.
If you link to table, then Access can figure out which column is the PK, and will set this for you. But SQLServer does not have a setting, nor even the concept of a PK column for a view, and thus you have to select the PK during linking using the GUI, or as noted, you can in code execute the above command that tells access which column to use as the PK, and as noted, that command does not in fact even create an index, but that command is ONLY to tell Access client side which column to see/use as the PK.
You can for views that don't require you to "update" the data. So, a linked view without you selecting (or better said "setting") the PK column will be read only.
So, if you using the view for a combo box, or say just a report? Then you don't care, and don't need to set the PK for that view, and it will be "read only". So this means that you ONLY need to set the PK column for a view if you need to update that view (say in place of updating the base table that the view is based on).
So, in summary:
that create index command does not actually create an index.
That create index command is ONLY required if you need a linked view that allows Access client side to update such views. Without the setting, then the linked view will be read only. So the purpose, the act, the role, the "thing" that create index does on the linked view? It is ONLY to tell Access what column is to be used for the PK - it does not actually create an index anywhere - including NOT creating one in Access client side. (So, ONLY purpose is for TELLING access which column to use for the PK. Can't really say why they use that command that way but best guess was no other way existed to tell Access what column to use for the PK - so we use that command).
If you use the linked table manager, and re-fresh the table links? Access WILL remember the PK settings for a view. However, if during linking you change the database that the linked tables point to? Then the PK settings in views will be lost during that re-linking process. (and then you have to re-execute those commands to re-tell Access which column in the linked view is to be seen/used as PK column.
You don't need to ever create an index client side for Access in regards to linked tables, or views - all indexing is automatic, and if an index exists on the server table, it will and can be used.
So, create index command is HOW you setup a PK column for linked views. In all other cases (linked tables - but not a view), then that command is not required, and ANY and all existing indexes that exist and were created on the server side table will be used (and thus no need to try or create an index in Access, since all such indexes are handled by the server side - Access has no say, nor even control over how SQLServer uses indexes). But, a correct use of index on a SQLServer table will automatically be used by Access in the requests it makes to SQLServer. But that "job" of indexing is 100% managed by the server - not Access.
I have in Microsoft Access a linked table to an ASE Server.
On the server side, the table has no primary key or identity columns.
And has a trigger on insert that validates new entries, so that when the entry is not validated it deletes the entry from the table and writes to "table"_ERR to let the users know what error was produced.
When linking it to Access a composite key is created using 10 columns.
I have this same setup in 10 different tables (all with triggers all linked to Access)
In this particular table when trying to insert/append records to the table through Access i always get the error message:
Single-row update/delete affected more than one row of a linked table. Unique index contains duplicate values.
This error occurs when both table and table_ERR are empty and i'm only trying to insert 1 record.
If I disable the trigger i have no problem inserting records through Access
I have similar triggers in other tables that are working correctly.
What can be causing this issue and does anyone know how to solve this?
I have read that MS Access can mess up the ##identity, even so none of the solutions presented online seem to work.
links : https://groups.google.com/forum/#!msg/microsoft.public.sqlserver.programming/McHdRpPKMhs/SlyObU8w7JMJ
Stop Access from using wrong identity when appending to linked table on SQL server
Thanks in advance.
EDIT: if i try to insert the records directly from a management software (like Aqua Data Studio) there are no erros
Without knowing more specifics about your data itself, it is difficult to say why this might be happening.
However, it sounds like in this specific instance for this specific linked table, your 10 columns are not unique enough to prevent non-distinct rows from being selected.
Suggested fixes:
Add a primary key. Honestly, probably the best and easiest choice.
If for some reason you cannot add a new column to (or alter) your table; you may be able to re-link your table, and re-choose your 10 columns so that they are more unique.
Beyond that, I think we would need more information.
Just out of curiousity, what is the reason for having no key?
Finally reached data migration part of my Project and now trying to move data from MySQL to SQL Server.
SQL Server has new schema (mapping is not always one to one).
I am trying to use SSIS for the conversion, which I started learning today morning.
We have customer and customer location table in MySQL and equivalent table in SQL Server. In SQL server all my tables now have surrogate key column (GUID) and I am creating the same in Script Component.
Also note that I do have a primary key in current mysql tables.
What I am looking for is how I can add child records to customer location table with newly created guid as parent key.
I see that SSIS have Foreach loop container, is this of any use here.
if not another possibility that I can think of is create two Data Flow Task and [somehow] just before the master data is sent to Destination Component [Table] on primary dataflow task , add a variable with newly created GUID and another with old PrimaryID, which will be used to create source for DataTask Flow for child records.
May be to simplyfy , this can also be done once datatask for master is complete and then datatask for child reads this master data and inserts child records from MySQL to SQL Server table. This would though mean that I have to load all my parent table records back into memory.
I know this is all too confusing and it is mainly because I am very confused :-(, to bear with me and if you want more information let me know.
I have been through may links that i found through google search but none of them really explains( or I was not able to uderstand) how the process is carried out.
Please advise
regards,
Mar
** Edit 1**
after further searching and refining key words i found this link in SO and going through it to see if it can be used in my scenario
How to load parent child data found in EDI 823 lockbox file using SSIS?
OK here is what I would do. Put the my sql data into staging tables in sql server that have identity columns set up and an extra column for the eventual GUID which will start out as null. Now your records have a primary key.
Next comes the sneaky trick. Pick a required field (we use last_name) and instead of the real data insert the value form the id field in the staging table. Now you havea record that has both the guid and the id in it. Update the guid field in the staging table by joing to it on the ID and the required field you picked out. Now update the last_name field with the real data.
To avoid the sneaky trick and if this is only a onetime upload, add a column to your tables that contains the staging table id. Again you can use this to get the guid for inserting to related tables. Then when you are done, drop the extra column.
You are aware that there are performance issues involved with using GUIDs? Make sure not to make them the clustered index (as the PK they will be by default unless you specify differntly) and use newsequentialid() to populate them. Why are you using GUIDs? If an identity would work, it is usually better to use it.
Can I do this?
The reason I want to do this is, I am importing data from a csv file to access, and during the import process it creates a lot of problems with the autonumber in access.
The tables are not going to be linked in anyway
A primary key is not mandatory. If you don't want one, don't add one!
Yes, but consider adding it back when you're done importing. Otherwise you may run into issues when trying to do edits, deletes, etc. If you want to be able to edit or delete the records after you've imported, then you'll want a primary key. If you just need read-only access to the data after import, then you should be fine without a primary key.
Is there a certain data type on phpmyadmin that works like in ms access that if you don't specify a primary key, ms access will prompt to create a primary key named 'ID' which will then be incrementing(1,2,3..) as you are adding more records to the database.
I'm assuming you're referring to MySQL, the database, and not phpmyadmin, the web-app used to interface with it. You can use AUTO_INCREMENT to do this very thing. See the CREATE query on the documentation page for a simple and succinct example how of to accomplish this.