How do I make a non-partition field of the table mandatory in Cassandra? I can't find anything in the documentation unfortunately
There isn't any NULL or NOT NULL constraints as you'd find in a relational database. The only requirement is to have a primary key.
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I am using talend for ETL I don't have enough experience in this, I am having two tables for example- account and account_roles account table is having id, name, password etc fields and account_roles table is having account_id which is f.k to account table's pk. and one more field.
Both the fields in account_roles are having duplicates, I want to save account_roles in destination with update and insert logic using talend.
But I am getting error as I don't have any table that can be treated as primary key in the account_roles table, so talend can't update or insert it.
How I deal with this situation I tried tDBOutput advance option use_field_option but still it requires unique entries.
Is there any possible solution to this issue, I also want to know if I can make table Foreign key in the account_roles table will it work then? If yes then How to make F.k in talend OPen studio is my second question.
Attaching Snapshots of my tables and tMap below -
I want to know the way I can put my tables into database if I don't have any primary key! Kindly help me.
First question
I think you should place the primary key in the physical account_roles table. Talend will use the key indication of the dbOutput component, and the physical key of the table.
In order to delete duplicates rows, you can also use a tUniqRow before the dbOutput: The key you indicate in the UniqRow is not directly linked to the database; this is only the key on which tUniqRow will be based.
Second question
It's not possible to delegate the f.k. verification to Talend. But you can do this verification in your database by placing foreign keys in your table. If an id is not present in the reference table, the database returns an error that is returned by Talend.
I try to update column type from DateTime(TZ) to DateTime, but it is key column and couldn't be changed. Drop/create table doesn't have any result - looks like metadata stored in ZK.
Can I change table structure (I can drop/create table) without changing ZK records? Or it is required to remove meta from ZK?
You need to drop a table at all replicas. If you lost a replica and did notdrop their table you need to clean ZK manually.
Or you can just use another ZK path. Table name does matter.
KEY ix_email_address (address) how to implement the MySQL constraint in Hive ?
Hive doesn't contain any primary/foreign key notions. You need to find another way to implement those constraints. Look here.
There is a name field in the UI which is also the primary key column in the underlying table. There is a requirement to make that field editable in the UI. There should be an ID which should serve as the primary key, but there isn't and now it is not feasible to introduce any ID column.
Is there any alternate design idea which can be used in such a scenario ?
The UI is in Swing and DB is Oracle.
First of all, I don't know, who thinks Name field can be Primary Key. That's the wrong database design ever.
Yes, you better change it to some ID column as Primary Key and that shouldn't be updated in future. Since, you can't have multiple Primary Key. So, you need to perform some circus here.
You need to drop existing Primary Key first. Since, you can't have multiple Primary Key in single table.
Create your ID column and allow NULL
Then, update this column with sequence.
Once your ID column gets populated, you need to create Primary Key on this column.
You can only have one primary key, but you can have any number of unique indexes on a table. So let the existing primary key be the immutable primary key and have the application use this key internally for everything. Add another column to the table and create a unique index on it. Let the users modify this other field.
Another alternative would be to declare all child tables with foreign keys ON UPDATE CASCADE. That way, any update to the primary key will cascade to the child tables. Once implemented in production, quit the company and run fast in the other direction and write an article about how you were the first person ever to use ON UPDATE CASCADE in a production setting.
I have a table with a long value as primary key.
Now i think that oracle by default will create a index on it.And i dont need to
create a index explicityly.
The question is :Is primary key by default indexed by oracle in this case?
Yes, a primary key (or any unique column constraint) will create an index, if there is not already one present.
This is the case for almost all databases. Otherwise the uniqueness constraint cannot be efficiently enforced.