So as apart of of a project I am doing I have been restricted on the editing of the Database from which I am building this application. I can not directly make changes to the Database from the SQL Command Prompt, all changes and new entries have to be made through Apex. Just clarifying this.
So I have a table TAXIUSER that has a primary key of TAXIUSERID. The primary key format for data currently in the Database is as follows:
UID0001
UID0002
and so on. Currently the user has to manually enter a new primary key each time they add an entry to the table. How through the Apex application solely (I can't use SQL Workshop either!) can I achieve something that would allow the user to not have to manually enter the primary key and preferably have it increment still in the above format.
EDIT: Sorry I should clarify I am using an Form on a Table with Report and version 11g.
You can do this by creating a read only item with a default value (or a computation) of
SELECT
'UID'||LPAD(MAX(SUBSTR(taxiuserid,4) + 1),4,0)
FROM
taxiuser;
Note that your prerequisites (no access to db) are forcing this to be a flawed approach:
Errors out with primary key constraint violation if 2 or more users are creating records at the same time. You could minimize the risk by calculating the new value on submit but then the user will not see the value when they're creating the user
Only works for the first 9999 users
Edit: If you use the computation after submit method, you will need to add condition to allow edits to made to existing entries. Otherwise the computation will attempt to change the primary key of that entry causing an error. To do this simply add a condition of Value in Expression 1 is Null, then specify the column from which the data is being entered into the table, like as follows:
P8_TAXIUSERID
This essentially means the computation will only ever attempt a value to TAXIUSERID when P8_TAXIUSERID (the column from which your are entering the data) contains a null value.
Related
I am writing RESTful API using cakephp 3.6 for SQL Server 2012. Some API's created and working fine.
But unfortunately not for one table. This table have primary key but its value is not auto incremented. When I am assigning its value API its generating error
SQLSTATE[23000]: [Microsoft][ODBC Driver 11 for SQL Server][SQL Server]Cannot insert the value NULL into column 'Id', table 'AccountsLive.dbo.Books'; column does not allow nulls. INSERT fails
I can't keep its primary key auto incremented.
When I create view to add it from browser. It does not create field for Id field. Then I try to create input field for Id field, its not going to display it on books input form.
Please help me to solve this issue, I will be thankful to you.
The assumption is that your id columns will be auto-incrementing. If there's a good reason(*) why you can't do that here, you'll need to add the input field (as you found), and also add it to the _accessible list in the Book entity.
(*) The number of situations where having your id column not auto-incrementing (and not a UUID) makes sense is really very small. Be very sure that this really does apply to you, as it moves all responsibility for avoiding overwriting records due to duplication onto you instead of the database.
I have a table in my SQL Server. Currently I am using the identity column to uniquely identify each record but my changing needs required a unique key generated in a certain format (as specified by my client). I have tried to generate the unique key from my application by appending a unique integer (that is incremented on every insert) to the format specified my client is not satisfied with my current solution.
It would be great if I can be directed to a better technique to solve my problem rather then my current solution.
The format is like:
PRN-YEAR-MyAppGeneratedInt
Basically, keep the current identity column. That is the best way for you to identify and manage rows in the table.
If the client needs another unique key, then add it. Presumably, it will be a string (given that it has a "format"). You can possibly create the key as a generated column. Alternatively, you may need to use a trigger to calculate it.
In general, integers are better for identity columns, even if end users never see them. Here are some advantages:
They encode the ordering of row insertion in the database. You can, for instance, get the last inserted row.
They are more efficient for foreign key references (because numbers are fixed-length and generally shorter than strings).
They make it possible to directly address a row, when data needs to be fixed.
You can create a SEQUENCE to serve your purpose which were introduced in SQL Server 2012. A real detailed explanation about SEQUENCE can be found here.
Hope this helps :)
As per you specified in the comments the format let me also give you an example that how you can solve your problem using a sequence:
First create a sequence like:
CREATE SEQUENCE SeqName
AS int
START WITH 1
INCREMENT BY 1
CYCLE
CACHE
Next you can use this sequence to generate your desired unique key in you app program.
Get the next value for sequence "SELECT NEXT VALUE FOR SeqName;"
Create a string using the value like :String key= "PRN"+year+SeqValue;
Finally store this string as your unique key in your Insert statement.
You can write the application code as per you need :)
You could create a Computed Column and just append the identity
('Custom_'+CONVERT(varchar(10),iden))
I'm learning SQLite from this webiste: SQLite Tutorial.
I was reading the article they had on the AUTOINCREMENT command.
My question had to do with their explanation of why this feature is useful:
The main purpose of using AUTOINCREMENT attribute is…
To prevent SQLite to reuse value that has not been used or from the previously deleted row.
I'm confused about this explanation as it doesn't explain in detail what the implications of this statement is.
Could someone please give more detail about what happens in the background, if this feature is implemented differently for different platforms or specific packaging of the engine in different packages (npm packages etc.).
Also, more importantly, give examples of use cases where using this feature would be necessary and what would be both the proper and improper ways of using it.
Thanks to all!
To prevent SQLite to reuse value that has not been used or from the
previously deleted row.
AUTOINCREMENT property ensure that newly generated id will be unique that will be not from any already used id in that column or should not be from id that has been deleted. It is mostly used in primary key of table where we need unique property which has not been used so far.
In most of relational database, there is AutoIncrement property but in Oracle, I've seen Sequence which similarly acts AutoIncrement property.
For e.g : if you have 10 rows which has AutoIncrement column called id and has value from 1 to 10. Now, you delete all rows and insert new one, then new row will have id = 11 becase 1 to 10 has already been used. You do not need to specify id value as it automatically fills up new row id value by checking previous inserted value.
This feature is usually being used on the table's primary key (I personally prefer to name it ID), like this:
CREATE TABLE MYTABLE(
ID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
...
);
If you are learning SQLite, you should know that the table's primary key absolutely mush be unique for each record in this table.
So if you are inserting a record to the table without AUTOINCREMENT on its primary key, the database will force you to specify ID of each new record.
If there are already some records in your table, you may ask yourself a question like "What ID whould I put in the record to ensure that it will be unique?"
This is what AUTOINCREMENT was created for. If AUTOINCREMENT is set on the table's primary key, you don't longer need to specify it when inserting a record, so you don't longer need to think what ID to put there.
Now how does it work. If AUTOINCREMENT is set on the table's primary key, a special number of added records (let's name it as a variable "added") is being stored along with the table's data in the database. When you issue the INSERT command with this table, its ID will be calculated like
added + 1
And the added variable will be incremented (autoINCREMENT)
Initially, added's value is 0.
For example, as Akash KC already said, if 10 records were added to the table, the next record's ID will be 11.
The detail is that AUTOINCREMENT doesn't mind deletions - if you take an empty table, add 10 records to it, delete one of them with ID 5 (for example) and then add a new one, its ID will be 11 as well.
I have tried 2 different online sql table editors,
Universal Table Editor &
Table Smart Editor
When viewing the database using the tools above, if there is a primary key field defined in my tables, it is uneditable. At the beggining I was thinking that it was related to table editor, however 2 different editors resulted the same problem, so I am thinking it is related to sql server.
I am currently using SQL Server 2005.
Here are the images for my editors and my database properties:
Normally, an error message will accompany a failed attempt to modify a database value. What was the message?
This sounds like the primary key is set up as an auto-numbered identity. In this case, the value is determined by the database automatically when each row is created. And you cannot edit this value.
The editors you're using seem to have been built with certain assumptions - that primary key values never change, and furthermore that they're always system generated.
Neither assumption is generally true. Whilst it's often described as desirable that primary key values never change, a good tool should not assume this to be true. Nor should it assume that primary key values will always be auto-generated.
There are some mitigating features built into SQL to deal with primary keys that do change - notably, the CASCADE features of FOREIGN KEY constraints.
Currently I'm performing a migration from a microsoft access database to an SQL Express 2010 database.
Basically, I have an Access application that searches a customer database. The access app is developed in 2 parts. An access front end on each client called application.mdb and a data backend on a windows 2008 server called data.mdb. The application.mdb has 3 linked tables to data.mdb. which holds customers and contracts and items. The customer table relates to the contracts table (one to many) and the contracts table relates to the items table (one to many)
I imported the tables from the data.mdb into the sql tables by the same name and created the same relationships and configured them to cascade. I then created an obdc connection on the clients and updated the 3 linked tables in application.mdb to point to the tables on the sql server.
I start the application and everything seemed to work great, I can see all the data perfectly and the performance increase was well worth the effort.
Then I found a problem, when I add a new customer to the database it autonumbers the customer table and the contracts table but not the items table.... Thus if I attempt to alters any of the items in the items table for new customers I can not. I get the following error "cannot add record(s); primary key for table "items" not in recordset" which makes sense because SQL had not autonumbered the items table.
I can't understand why....
Any help would be greatly appreciated.
Well, just manually adding record direct in the items view should tell you if the autonumber is working. You MUST get the autonumber working when you edit + use in direct table view.
As always these kinds of issues comes down to the details. One thing that's different when using a SQL based backend compared for access applications is the generation of auto numbers (primary key) does not occur on server based systems until record is actually saved. When working with the jet based back end, the auto number is available the instant the record is dirtied.
So I would check if you have some type of code or event running in the application that is attempting to use as primary key value before the record been actually saved.
Usually access does a pretty good job. For example when you build a form in access, and then have a sub form in access to edit child records (and a child table), then as a rule when the focus switches from a main form to a sub form, access will force a save of the main record. This thus means the primary key (auto number column) is now available for correct functioning of the relationship. Access can and will use this PK value and insert this value into the foreign key value column in this child table for you.
However access will only do above for you WHEN you correctly set up the link master and link child settings in the sub form control. As a general rule when building forms in regular access, Access can detect the settings required and insert the correct values into the link master and link child settings for you. However, the detection of the FK column will not occur with linked tables.
So when you use SQL server, you have to edit and set these values manually in the sub form control. So I would check your link master and link child settings in the sub form you're using to edit this data, and ensure that the correct values are set. If this is VBA code, then ensure the record is actually saved before attempt to use and grab a PK value.
I should point out that even in non SQL server based applications, it is the setting up of the link master + child settings in the sub form that allows access to setup and maintain this foreign key value for you. So access is always had the ability to insert these values for you, and it'll do so with you about having to write any code at all. So during the editing process to insert and maintain these values Access does all of the work for you (so it's not the data engine that inserts these FK values for you, but the user interface or in some cases code you write)
So access will not setup and insert these correct values unless you set up the link master + child settings in that sub form control.
I would simply check if your link master and child master settings are correct in any sub form control you are using here.
This sounds like a stupid answer but check the Items table to be sure that auto-numbering is turned on.
One of the things I would suggest whenever you migrate a Jet/ACE database to SQL Server is to thoroughly review the database design, e.g.: the implementation of keys and constraints, choice of data types, choice of indexes, etc. Jet/ACE is a very different thing to most SQL DBMSs so you shouldn't assume that a database design that worked well for Jet/ACE is automatically suitable for a SQL DBMS. Upsizing wizards won't always identify every possible issue.
In SQL Server the nearest equivalent of an "auto-number" is the IDENTITY property. Check to be sure which columns are IDENTITY in your tables and create an IDENTITY column if you need one.