I've created a simple table in Oracle 12c like so:
CREATE TABLE TEST
(
ID NUMBER GENERATED ALWAYS AS IDENTITY,
TEXT VARCHAR2(2000 CHAR),
CONSTRAINT ID_PK PRIMARY KEY (ID)
);
Then I linked it in MS Access using ODBC driver. The problem is that when I input value into TEXT and click away both ID and TEXT show #Deleted. My value gets recorded in the database but I have to requery in MS Access in order to see it.
I also noticed that if I change the datatype of TEXT field to NUMBER, it works fine. After saving the record in MS Access both auto generated ID and value in TEXT field are there. I don't have to requery anything.
This happens only when inserting. Updating works just fine.
Please advise.
So, it would appear you already found the solution, but this is more of an explanation as to why it works that way. Simply speaking, if the base-table uses non-integer values as primary keys, Access rounds these integers to the nearest whole number and then (since it was not a numeric value) Access can no longer find the applicable records. So, changing the data type from TEXT to INTEGER in the table structure would give you your desired result.
Alternatively, if you're using a query to run through these, if you cannot change the keys in the Oracle table then altering the Access query type to a snapshot (in the query properties) will also bypass this problem. But from the sounds of it, this is not how you are utilizing the data.
In my case, the Oracle ODBC driver (using the rather old version 11.02.00.01 that otherwise works ok and Microsoft Access 2016 32Bit) seems to use the unique indices and not the primary key constraint for determining the primary key.
I had a field with NUMBER(11) as PK with an unique index, then added a VARCHAR2 field with another unique index. The name of the index of the VARCHAR2 field was alphabetically before that of the NUMBER field.
Now, the linked table in Microsoft Access showed the VARCHAR2 field as primary key and I had the problem with '#Deleted' appearing after entering & saving a record as you describe.
After renaming the unique index on the NUMBER field in Oracle to be alphabetically before that of the VARCHAR2 field and re-linking the table in Microsoft Acces, the NUMBER field was the primary key again in Microsoft Access and the '#Deleted' problem was solved.
Related
I am new to Oracle sql, but I have some experience with MSSQL. I was sent a script to create some tables, but because of the BLOB columns, I am getting a couple errors when I try to limit the size.
I tried asking my co-workers about this, but they aren't sure either. This was basically grabbed from somewhere else, so they're not sure how to fix this.
Essentially, the table looks something like this (table and column names were changed):
CREATE TABLE table1
(
ID CHAR(32),
NAME CHAR(50),
KEY $(BLOB)(64),
BUFFER $(BLOB)(20),
SORTNO NUMERIC(8) CONSTRAINT UK_WIU UNIQUE,
CONSTRAINT PK_ID PRIMARY KEY (ID)
)
;
When running this, I get the error "invalid character" because of the dollar sign ($). But if I change data type to BLOB(64), I get an error saying "missing right parenthesis." If I just do "BLOB," it runs fine. Is there any way to define the length for BLOB?
Thank you
BLOB column's size can't be restricted. It allows you to store up to [(4 gigabytes - 1) * (database block size)] data, and that's it. If you need less than that, fine, no problem.
More about BLOB (and other Oracle 18c datatypes) here: https://docs.oracle.com/en/database/oracle/oracle-database/18/sqlrf/Data-Types.html#GUID-1A71C635-188E-4EC9-B821-1DBEC2B45451
Table you meant to create would in Oracle look like this:
SQL> create table table1
2 (id varchar2(32) constraint pk_id primary key,
3 name varchar2(50),
4 sortno number(8) constraint uk_wiu unique,
5 key blob,
6 buffer blob
7 );
Table created.
SQL>
Yet another objection regarding your code: don't use CHAR but VARCHAR2 (unless you have to); CHAR will right-pad values with spaces, up to the maximum length of the column.
No, columns are just defined as a CLOB or BLOB.
There is no size associated with the column. You can put in something as big or small as you like, with a few restrictions.
"Maximum size: (4 GB - 1) * DB_BLOCK_SIZE initialization parameter (8 TB to 128 TB)"..as of 11g of Oracle.
To limit the size, you could, do so at the application layer - prevent folks from uploading files larger than X, although someone with DB access could do this.
You could write a stored procedure for handling INSERT/UPDATES, and have logic in there to prevent DML if the size is 'too large.'
You might be able to do a check constraint using a function call to get the length of the lob...an example here
I'm using APEX 5 for the first time and having issue trying to insert items into my blob table.
I searched for many guides about creating File Browse's storage type to BLOB columns, which allows me to add MIME_TYPE, FILENAME, and CHARSET etc into my table. I am trying to create both upload and download feature.
But one thing that's been really confusing is creating DML processes, I could not understand where they getting their primary key item from, I somewhat understand that the DML primary key column are supposed to be my table's primary key?Errors keep coming up when I try to upload.
: https://i.stack.imgur.com/pj0G0.png
Any kind of help or tips would be greatly appreciated!
Below is my table to store blob
CREATE TABLE "MATERIALS"
( "ID" NUMBER NOT NULL ENABLE,
"MATERIAL_NAME" VARCHAR2(400),
"FILENAME" VARCHAR2(350),
"M_COURSE_ID" VARCHAR2(68),
"MIME_TYPE" VARCHAR2(255),
"DOC_SIZE" NUMBER,
"CHARSET" VARCHAR2(128),
"LAST_UPDATE_DATE" DATE,
"CONTENT" BLOB,
CONSTRAINT "MATERIALS_PK" PRIMARY KEY ("ID")
USING INDEX ENABLE
) NO INMEMORY
You'll need a item on your page to hold the id field. Your first process will populate it. I'm guessing you have a sequence?
Create a Hidden item, I'll call it P1_ID.
Your first process will populate it if it's empty. Create a process at the Processing step with a body of:
apex_util.set_session_state( 'P1_ID', mysequence.NEXTVAL );
Your DML process must run after this step, so drag them around or change the sequence if necessary.
Now set the Primary Key Item value to P1_ID in your DML process.
I am using Oracle 12c and I have an IDENTITY column set as GENERATED ALWAYS.
CREATE TABLE Customers
(
id NUMBER GENERATED ALWAYS AS IDENTITY,
customerName VARCHAR2(30) NULL,
CONSTRAINT "CUSTOMER_ID_PK" PRIMARY KEY ("ID")
);
Since the ID is automatically from a sequence it will be always unique.
Do I need a PK on the ID column, and if yes, will it impact the performance?
Would an index produce the same result with a better performance on INSERT?
No, you don't need a primary key necessarily, but you should always provide the optimiser as much information about your data as possible - including a unique constraint whenever possible.
In the case of a surrogate key (like your ID), it's almost always appropriate to declare it as a Primary Key, since it's the most likely candidate for referential constraints.
You could use an ordinary index on ID, and performance of lookups will be comparable depending on data volume - but there is virtually no good reason in this case to use a non-unique index instead of a unique index - and there is no good reason in this case to avoid the constraint which will require an index anyway.
Yes, you always should have a Uniqueness constraint (with rare exceptions) on an ID column if indeed it is (and should be) unique, regardless of the method by which it is populated - whether the value is provided by your application code or via an IDENTITY column.
I'm trying to generate a sorted GUID as a primary key in Oracle. In SQL Server I could use one of the following to sort the rows physically
By clustered primary key as a unique identifier.
By NEWSEQUENTIALID.
I have searched for an Oracle equivalent but failed to find a solution. I know about Is there a way to create an auto-incrementing Guid Primary Key in an Oracle database?, but there's no indication whether SYS_GUID() is sorted.
How could I create a sequential primary key in Oracle?
If you want to create a GUID then SYS_GUID() is what you should be using, you can create this in a table as per the linked question. It's unclear from the documentation whether SYS_GUID() is incrementing. It might be but that's not really a statement that imparts trust.
The next part of your question (and some comments) keeps asking about clustered primary keys. This concept does not exist in the same way in Oracle as it does in SQL Server and Sybase. Oracle does have indexed organized tables (IOT) ...
... a table stored in a variation of a B-tree index structure... rows
are stored in an index defined on the primary key for the table. Each
index entry in the B-tree also stores the non-key column values. Thus,
the index is the data, and the data is the index.
There are plenty of uses for IOTs but it's worth bearing in mind you're altering the physical structure of the database on the disk for "performance reasons". You're doing the ultimate of all premature optimizations using something that has both negative and positive aspects. Read the documentation and be sure that this is what you want to do.
I would generally use an IOT only when you don't care about DML performance but when you do a lot of range scans, or you need to order by the primary key. You create an IOT in the same way as you would an ordinary table, but because everything you want is now part of the table everything goes in your table definition:
create table test_table (
id raw(32) default sys_guid()
, a_col varchar2(50)
, constraint pk_my_iot primary key (id)
) organization index;
It's worth noting that even with an IOT you must use an explicit ORDER BY in order to guarantee returned order. However, because of the way this is stored Oracle can table a few short cuts:
select *
from ( select *
from test_table
order by id )
where rownum < 2
SQL Fiddle.
As with everything, test, don't assume that this is the structure you want.
Oracle has as SYS_GUID() function, which generates a 16-byte RAW datatype. But, I'm not sure what you mean by "sorted GUID". Can you elaborate?
Do you mean you need each generated GUID to sort "after" the previously generated GUID? I looked at the SYS_GUID() function, and it seems to generate GUIDs in sorted order, but looking at the documentation, I don't see anything that says that is guaranteed.
If I understand your question correctly, I'm not sure it's possible.
You may be able to use SYS_GUID() and prepend a sequence, to get your desired sort order?
Can you explain more about your use case?
Adding the following in response to comment:
Ok, now I think I understand. What I think you want, is something called an IOT, or Index Organized Table, in Oracle. It's a table that has an index strucure, and all data is clustered, or grouped by the primary key. More information is available here:
http://docs.oracle.com/cd/E16655_01/server.121/e17633/indexiot.htm#CNCPT721
I think that should do what you want.
I'm trying to create a new row in a table. There are two constraints on the table -- one is on the key field (DB_ID), the other constrains a value to be one of several the the field ENV. When I do an insert, I do not include the key field as one of the fields I'm trying to insert, yet I'm getting this error:
unique constraint (N390.PK_DB_ID) violated
Here's the SQL that causes the error:
insert into cmdb_db
(narrative_name, db_name, db_type, schema, node, env, server_id, state, path)
values
('Test Database', 'DB', 'TYPE', 'SCH', '', 'SB01', 381, 'TEST', '')
The only thing I've been able to turn up is the possibility that Oracle might be trying to assign an already in-use DB_ID if rows were inserted manually. The data in this database was somehow restored/moved from a production database, but I don't have the details as to how that was done.
Any thoughts?
Presumably, since you're not providing a value for the DB_ID column, that value is being populated by a row-level before insert trigger defined on the table. That trigger, presumably, is selecting the value from a sequence.
Since the data was moved (presumably recently) from the production database, my wager would be that when the data was copied, the sequence was not modified as well. I would guess that the sequence is generating values that are much lower than the largest DB_ID that is currently in the table leading to the error.
You could confirm this suspicion by looking at the trigger to determine which sequence is being used and doing a
SELECT <<sequence name>>.nextval
FROM dual
and comparing that to
SELECT MAX(db_id)
FROM cmdb_db
If, as I suspect, the sequence is generating values that already exist in the database, you could increment the sequence until it was generating unused values or you could alter it to set the INCREMENT to something very large, get the nextval once, and set the INCREMENT back to 1.
Your error looks like you are duplicating an already existing Primary Key in your DB. You should modify your sql code to implement its own primary key by using something like the IDENTITY keyword.
CREATE TABLE [DB] (
[DBId] bigint NOT NULL IDENTITY,
...
CONSTRAINT [DB_PK] PRIMARY KEY ([DB] ASC),
);
It looks like you are not providing a value for the primary key field DB_ID. If that is a primary key, you must provide a unique value for that column. The only way not to provide it would be to create a database trigger that, on insert, would provide a value, most likely derived from a sequence.
If this is a restoration from another database and there is a sequence on this new instance, it might be trying to reuse a value. If the old data had unique keys from 1 - 1000 and your current sequence is at 500, it would be generating values that already exist. If a sequence does exist for this table and it is trying to use it, you would need to reconcile the values in your table with the current value of the sequence.
You can use SEQUENCE_NAME.CURRVAL to see the current value of the sequence (if it exists of course)