I have three tables:
Table1(id, name, no)
Table2(id, table1id, no)
Table3(id, table2id, no).
I have an object suitable for the structure of these tables and I want to save them in the database. While recording, I want to use the sequence of the first table in my second table. I will pull the sequence of my first table from the database. I will save tables 2 and 3 in the same way. I want to save these transactions in my oracle database using sqlkata, dapper in .net environment.
I tried pulling the sequence value and setting it each time.
Related
I have the following scenario and need to solve it in ORACLE:
Table A is on a DB-server
Table B is on a different server
Table A will be populated with data.
Whenever something is inserted to Table A, i want to copy it to Table B.
Table B nearly has similar columns, but sometimes I just want to get
the content from 2 columns from tableA and concatenate it and save it to
Table B.
I am not very familiar with ORACLE, but after researching on GOOGLE
some say that you can do it with TRIGGERS or VIEWS, how would you do it?
So in general, there is a table which will be populated and its content
should be copien to a different table.
This is the solution I came up so far
create public database link
other_db
connect to
user
identified by
pw
using 'tns-entry';
CREATE TRIGGER modify_remote_my_table
AFTER INSERT ON my_table
BEGIN INSERT INTO ....?
END;
/
How can I select the latest row that was inserted?
If the databases of these two tables are in two different servers, then you will need a database link (db-link) to be created in Table A schema so that it can access(read/write) the Table B data using db-link.
Step 1: Create a database link in Table A server db pointing to Table B server DB
Step 2: Create a trigger for Table A, which helps in inserting data to the table B using database link. You can customize ( concatenate the values) inside the trigger before inserting it into table B.
This link should help you
http://searchoracle.techtarget.com/tip/How-to-create-a-database-link-in-Oracle
Yes you can do this with triggers. But there may be a few disadvantages.
What if database B is not available? -> Exception handling in you trigger.
What if database B was not available for 2h? You inserted data into database A which is now missing in database B. -> Do crazy things with temporarily inserting it into a cache table in database A.
Performance. Well, the performance for inserting a lot of data will be ugly. Each time you insert data, Oracle will start the PL/SQL engine to insert the data into the remote database.
Maybe you could think about using MViews (Materialized Views) to replicate the data via database link. Later you can build your queries so that they access tables from database B and add the required data from database A by joining the MViews.
You can also use fast refresh to replicate the data (almost) realtime.
From perspective of an Oracle Database Admin this would make a lot more sense than the trigger approach.
try this code
database links are considered rather insecure and oracle own options are having licences associated these days, some of the other options are deprecated as well.
https://gist.github.com/anonymous/e3051239ba401e416565cdd912e0de8c
uses ora_rowscn to sync tables across two different oracle databases.
I have a question about how to change relationships between tales in an Oracle database while preserving existing data.
Let's say I want to represent People and Employers such that each person works for a single employer. I do this with a PERSON table and an EMPLOYER table with a 1:M relationship of EMPLOYER to PERSON. The PERSON table had columns ID, NAME, and EMPLOYER_ID, and the EMPLOYER table had columns ID, NAME, AND LOCATION.
If I wanted to update this schema so a PERSON can work for more than one EMPLOYER, I could add a PERSON_EMPLOYER table with columns for each ID.
Could anyone give some pointers on the most sensible way to do this and move my existing data in? I think I can add a join table, but I'm not sure how to populate it with existing employer:employer data. After that I guess I remove EMPLOYER_ID column from PERSON.
Should I just be backing up the database and doing this operation in a script?
Thank you so much.
Having a backup is always a good idea.
But in my opinion transferring data from one table to another it is quite reliable operation. You do not necessary make a script, just do it step by step and check changes.
Create a new PERSON_EMPLOYER table
Copy existing data to PERSON_EMPLOYER table.
COMMIT data changes.
Check data in PERSON_EMPLOYER table
Drop EMPLOYER_ID column from PERSON table. (No need to remove the column immediately, it can be done later when you will be sure that everything is fine with the your data.)
For transferring data from PERSON table to PERSON_EMPLOYER table you can use simple INSERT
INSERT INTO employer_person (employer_id, person_id)
SELECT employer_id, person_id FROM person;
Do not forget COMMIT this operation!
I am trying to load the tables into oracle in-memory database. I have enable the tables for INMEMORY by using sql+ command ALTER TABLE table_name INMEMORY. The table also contains data i.e. the table is populated. But when I try to use the command SELECT v.owner, v.segment_name name, v.populate_status status from v$im_segments v;, it shows no rows selected.
What can be the problem?
Have you considered this?
https://docs.oracle.com/database/121/CNCPT/memory.htm#GUID-DF723C06-62FE-4E5A-8BE0-0703695A7886
Population of the IM Column Store in Response to Queries
Setting the INMEMORY attribute on an object means that this object is a candidate for population in the IM column store, not that the database immediately populates the object in memory.
By default (INMEMORY PRIORITY is set to NONE), the database delays population of a table in the IM column store until the database considers it useful. When the INMEMORY attribute is set for an object, the database may choose not to materialize all columns when the database determines that the memory is better used elsewhere. Also, the IM column store may populate a subset of columns from a table.
You probably need to run a select against the date first
I have a question: I have a table (say tableA) in a database (say dbA) and I need to mirror tableA as another table (say tableB) in another database (say dbB).
I know this can be done via (materialised) view or via informatica. But by problem is that I need to sync DDL as well. For example if a column is added in tableA, the column should automatically reflect in tableB.
Can this be done anyway directly via oracle or Informatica.
(or I will have to write a procedure to sync table on basis of all_tab_cols).
Yes, you could:
create another database as a logical standby database with Data Guard
use Oracle Streams
I would use (2) if you just need a single table in the other database or (1) if you need an entire schema (or more).
I have two tables, let's call them TableA and TableB. One record in TableA is related to one or more in TableB. But there's also one special record within them in TableB for each record from TableA (for example with lowest ID), and I want to have quick access to that special one. Data from both tables aren't deleted - it's a kind of history rarely cleared. How do that the best in terms of performance?
I thought of:
1) two-way relationship, but it will affect insert performance
2) design next table, with primary key as FK_TableA (for TableA record exactly one is "special") and second column FK_TableB and then create view
3) design next table, with primary key as FK_TableA, FK_TableB, make FK_TableA unique and then create view
I'm open for all other ideas :)
4) I'd consider an indexed view to hide the JOIN and row restriction
This is similar to your options 2 and 3 but the DB engine will maintain it for you. With a new table you'll either compromise data integrity or have to manage the data via triggers