Where/How are Oracle Column Aliases Declared? - oracle

I am trying to trace some information/primary keys in tables, and the normal mechanism we use to do this is through views that are nothing more than semantic layers on top of tables that have extremely cryptic column names.
As an example, the table looks like:
create table F3002_WH
(
ixtbm CHAR(9) not null,
ixkit NUMBER not null,
ixmmcu CHAR(36) not null,
ixcpnt NUMBER not null,
ixsbnt NUMBER not null,
ixbqty NUMBER not null,
ixcoby CHAR(3) not null
);
But the views turn each of these fields into readable names, such as "TYPE_BILL" instead of "ixtbm."
However, when I look at the DDL for the view:
CREATE OR REPLACE VIEW F3002_VIEW AS
SELECT
ixtbm, ixkit, ixmmcu, ixcpnt, ixsbnt, ixbqty, ixcoby
from F3002_WH;
I don't see the alias. I would have expected to see ixtbm as type_bill.
So my question is where does this alias come from, and how can I tie it to the original field name without turning this into a science project? I don't understand how it can be rendered when querying the view without being within the view code.
For what it's worth, I am using PL/SQL Developer, by All Around Automation. I strongly suspect it is not the culprit, but in the interest of full disclosure I thought to mention it.

CREATE VIEW myView (alias1, alias2) as select ixtbm, ixkit from f3002_wh;
I have to say though, if you can see the underlying view query then the obfuscation is a waste of time!
And what I assume is happening is that the DDL generated by your tool doesn't by default include the column list which is why you don't see it. If you dropped the view and rebuilt it with their generated DDL instead of using the script that originally created it and you would lose the aliases.
Their may be options on the DDL generator to include the column name list in views, but as I don't have that tool I cannot verify that. To do that they need to query ALL_TAB_COLUMNS rather than just showing the query from within the TEXT field of ALL_VIEWS.

Related

Switching between multiple tables at runtime in Oracle

I am working in an environment where we have separate tables for each client (this is something which I can't change due to security and other requirements). For example, if we have clients ACME and MEGAMART then we'd have an ACME_INFO table and MEGAMART_INFO tables and both tables would have the same structure (let's say ID, SOMEVAL1, SOMEVAL2).
I would like to have a way to easily access the different tables dynamically.
To this point I've dealt with this in a few ways including:
Using dynamic SQL in procedures/functions (not fun)
Creating a view which does a UNION ALL on all of the tables and which adds a CLIENT_ID COLUMN (i.e. "CREATE VIEW COMBINED_VIEW AS SELECT 'ACME' CLIENT_ID, ID, SOMEVAL1, SOMEVAL2 FROM ACME_INFO UNION ALL SELECT 'MEGMART' CLIENT_ID, ID, SOMEVAL1, SOMEVAL2") which performs surprisingly well, but is a pain to maintain and kind of defeats some of the requirements which dictate that we have separate tables for each client.
SYNONYMs won't work because we need different connections to act on different clients
A view which refers to a package which has a package variable for the active client. This is just evil and doesn't even work out all that well.
What I'd really like is to be able to create a table function, macro, or something else where I can do something like
SELECT * FROM FN_CLIENT_INFO('ACME');
or even
UPDATE (SELECT * FROM FN_CLIENT_INFO('ACME')) SET SOMEVAL1 = 444 WHERE ID = 3;
I know that I can partially achieve this with a pipelined function, but this mechanism will need to be used by a reporting platform and if the reporting platform does something like
SELECT * FROM FN_CLIENT_INFO('ACME') WHERE SOMEVAL1 = 4
then I want it to run efficiently (assuming SOMEVAL1 has an index for example). This is where a macro would do well.
Macros seem like a good solution, but the above won't work due to protections put in place to prevent against SQL injection.
Is there a way to create a macro that somehow verifies that the passed in VARCHAR2 is a valid table name and therefore can be used or is there some other approach to address what I need?
I was thinking that if I had a function which could translate a client name to a DBMS_TF.TABLE_T then I could use a macro, but I haven't found a way to do that well.
A lesser-known method for such cases is to use a system-partitioned table. For instance, consider the following code:
Full example: https://dbfiddle.uk/UQsAgHCk
create table t_common(a int, b int)
partition by system (
partition ACME_INFO,
partition MEGAMART_INFO
);
insert into t_common partition(acme_info)
values(1,1);
insert into t_common partition(megamart_info)
values(2,2);
commit;
select * from t_common partition(acme_info);
select * from t_common partition(megamart_info);
As demonstrated, a common table can be used with different partitions for different clients, allowing it to be used as a regular table. We can create a system-partitioned table and utilize the exchange partition feature with older tables. Then, we can drop the older tables and create views with the same names, so that older code continues to work with views while all new code can work with the common table by specifying a partition.

Trouble Understanding NEXTVAL and CURRVAL

I did search for a similar question, but if I overlooked an existing answer I am glad to be redirected there.
I am working to untangle an Oracle Stored Proceedure in a legacy system written by a long departed developer.
The focus of the proceedure is to upload user data into the existing table structure in a bulk collection and save keystroke time adding 1-x-1 records.
The procedure appears to work without error and the user group would like to expand it to allow additional data to load to separate but related tables.
The author is using the NEXTVAL and CURRVAL commands to add primary key information as new records are added using the CSV data.
But I am confused because my understanding of NEXTVAL/CURRVAL was that they required context and declaration to be used correctly.
For example the Proceedure has the following:
SELECT seq_site.nextval INTO v_curr
FROM DUAL;
UPDATE temp_table
SET site_id = seq_site.currval
However [SEQ_SITE] is not declared anywhere in the preceding lines of the Procedure.
Am I inferring correctly that the clause [SELECT seq_site.nextval INTO v_curr] is the declaration for [SEQ_Record_count]?
(...v_curr is declared an integer early in the procedure declarations btw...)

Oracle: Monitoring changes in v_$parameter

Long time user, first time "asker".
I am attempt to construct an Oracle procedure and/or trigger that will compare two tables with the MINUS operation and then insert any resulting rows into another table. I understand how to do the query in standard SQL, but I am having trouble coming up with an efficient way to do this using PL/SQL.
Admittedly, I am very new to Oracle and pretty green with SQL in general. This may be a silly way to go about accomplishing my goal, so allow me to explain what I am attempting to do.
I need to create some sort of alert that will be triggered when the V_$PARAMETER view is changed. Apparently triggers can not respond to changes to view but, instead, can only replace actions on views...which I do not wish to do. So, what I did was create a table that to mirror that view to essentially save it as a "snapshot".
create table mirror_v_$parameter as select * from v_$parameter;
Then, I attempted to make a procedure that would minus these two so that, whenever a change is made to v_$parameter, it will return the difference between the snapshot, mirror_v_$parameter. I trying to create a cursor with the command:
select * from v_$parameter minus select * from mirror_v_$parameter;
to be used inside a procedure, so that it could be used to fetch any returned rows and insert them into another table called alerts_v_$parameter. The intent being that, when something is added to the "alert" table, a trigger can be used to somehow (haven't gotten this far yet) notify my team that there has been a change to the v_$parameter table, and that they can refer to alerts_v_$parameter to see what has been change. I would use some kind of script to run this procedure at a regular interval. And maybe, some day down the line when I understand all this better, manipulate what goes into the alerts_v_$parameter table so that it provides better information such as specifically what column was changed, what was its previous value, etc.
Any advice or pointers?
Thank you for taking the time to read this. Any thoughts will be very appreciated.
I would create a table based on the exact structure of v_$parameter with an additional timestamp column for "last_update", and periodically (via DBMS_Scheduler) merge into it any changes from the real v_$parameter table and capture the timestamp of any detected change.
You might also populate a history table at the same time, either using triggers on update of your table or with SQL.
PL/SQL is unlikely to be required, except as a procedural wrapper to the SQL code.
Examples of Merge are in the documentation here: http://docs.oracle.com/cd/E11882_01/server.112/e26088/statements_9016.htm#SQLRF01606

DB2 duplicate key error when inserting, BUT working after select count(*)

I have a - for me unknown - issue and I don't know what's the logic/cause behind it. When I try to insert a record in a table I get a DB2 error saying:
[SQL0803] Duplicate key value specified: A unique index or unique constraint *N in *N
exists over one or more columns of table TABLEXXX in SCHEMAYYY. The operation cannot
be performed because one or more values would have produced a duplicate key in
the unique index or constraint.
Which is a quite clear message to me. But actually there would be no duplicate key if I inserted my new record seeing what records are already in there. When I do a SELECT COUNT(*) from SCHEMAYYY.TABLEXXX and then try to insert the record it works flawlessly.
How can it be that when performing the SELECT COUNT(*) I can suddenly insert the records? Is there some sort of index associated with it which might give issues because it is out of sync? I didn't design the data model, so I don't have deep knowledge of the system yet.
The original DB2 SQL is:
-- Generate SQL
-- Version: V6R1M0 080215
-- Generated on: 19/12/12 10:28:39
-- Relational Database: S656C89D
-- Standards Option: DB2 for i
CREATE TABLE TZVDB.PRODUCTCOSTS (
ID INTEGER GENERATED BY DEFAULT AS IDENTITY (
START WITH 1 INCREMENT BY 1
MINVALUE 1 MAXVALUE 2147483647
NO CYCLE NO ORDER
CACHE 20 )
,
PRODUCT_ID INTEGER DEFAULT NULL ,
STARTPRICE DECIMAL(7, 2) DEFAULT NULL ,
FROMDATE TIMESTAMP DEFAULT NULL ,
TILLDATE TIMESTAMP DEFAULT NULL ,
CONSTRAINT TZVDB.PRODUCTCOSTS_PK PRIMARY KEY( ID ) ) ;
ALTER TABLE TZVDB.PRODUCTCOSTS
ADD CONSTRAINT TZVDB.PRODCSTS_PRDCT_FK
FOREIGN KEY( PRODUCT_ID )
REFERENCES TZVDB.PRODUCT ( ID )
ON DELETE RESTRICT
ON UPDATE NO ACTION;
I'd like to see the statements...but since this question is a year old...I won't old my breath.
I'm thinking the problem may be the
GENERATED BY DEFAULT
And instead of passing NULL for the identity column, you're accidentally passing zero or some other duplicate value the first time around.
Either always pass NULL, pass a non-duplicate value or switch to GENERATED ALWAYS
Look at preceding messages in the joblog for specifics as to what caused this. I don't understand how the INSERT can suddenly work after the COUNT(*). Please let us know what you find.
Since it shows *N (ie n/a) as the name of the index or constraing, this suggests to me that is is not a standard DB2 object, and therefore may be a "logical file" [LF] defined with DDS rather than SQL, with a key structure different than what you were doing your COUNT(*) on.
Your shop may have better tools do view keys on dependent files, but the method below will work anywhere.
If your table might not be the actual "physical file", check this using Display File Description, DSPFD TZVDB.PRODUCTCOSTS, in a 5250 ("green screen") session.
Use the Display Database Relations command, DSPDBR TZVDB.PRODUCTCOSTS, to find what files are defined over your table. You can then DSPFD on each of these files to see the definition of the index key. Also check there that each of these indexes is maintained *IMMED, rather than *REBUILD or *DELAY. (A wild longshot guess as to a remotely possible cause of your strange anomaly.)
You will find the DB2 for i message finder here in the IBM i 7.1 Information Center or other releases
Is it a paging issue? we seem to get -0803 on inserts occasionally when a row is being held for update and it locks a page that probably contains the index that is needed for the insert? This is only a guess but it appears to me that is what is happening.
I know it is an old topic, but this is what Google shown me on the first place.
I had the same issue yesterday, causing me a lot of headache. I did the same as above, checked the table definitions, keys, existing items...
Then I found out the problem was with my INSERT statement. It was trying to insert to identical records at once, but as the constraint prevented the commit, I could not find anything in the database.
Advice: review your INSERT statement carefully! :)

When using Toad to create a view in Oracle, how can I store the formatted script also?

This question may be Toad specific. I have no idea how Oracle stores views, so I'll explain what happens when I use Toad. If I get an answer that is Oracle specific, so much the better.
I have created a rather complex view. To make it clearer, I have formatted the code nicely, and entered some comments where needed. When I need to make changes to the view, I use Toad's "describe objects" window, where I can find a script to recreate the view. The only problem is that all my formatting is gone. Comments before the select keyword (but after "create view xxx as") will also disappear.
If I enter this script to create a view:
create or replace view TestViewFormatting as
-- Here I have a long comment explaining the role of the
-- view and certain things to be aware of if changing it.
-- Unfortunately this comment will disappear...
select
name, --This comment will be kept
accountnumber --This also
from
debtable
where
name like 'S%';
Toad will display this when I describe it later:
DROP VIEW XXX.TESTVIEWFORMATTING;
/* Formatted on 04.07.2012 09:35:45 (QP5 v5.185.11230.41888) */
CREATE OR REPLACE FORCE VIEW XXX.TESTVIEWFORMATTING
(
NAME,
ACCOUNTNUMBER
)
AS
select name, --This comment will be kept
accountnumber --This also
from debtable
where name like 'S%';
Note that the first comment has disappeared, and that the format is totally different.
I suspect that Oracle doesn't store the code of the view, just some parsed version, and when Toad brings up the script, it reverses this parsed version and generates a script on the fly.
What will I have to do to make Toad/Oracle keep the original formatting?
(PS: I know I can change the settings for Toad's code formatter, but this is not what I want to do. Due to some questionable choices in my past, this particular view has several levels of inline views, and I need a very specific formatting to make it clear what happens)
select text from user_views
where view_name = 'YOUR_VIEW_NAME';
I've tested with:
create view z_v_test as
select
-- te
--st
* from
dual;
and it keeps even the blank line.
Another way is to use DBMS_METADATA:
select dbms_metadata.get_ddl('VIEW', 'YOUR_VIEW_NAME', user) from dual
This works not only for views, but also for (nearly) all kind of database objects (tables, triggers, functions, ...).

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