I would like to delete on record from impala table. Below I have used to delete the record from the table.
This is My Query :
DELETE FROM sample.employee_details WHERE sno=5 AND name='XYZ'AND age=26;
suggest the best way to remove a record from the table.
This is fine assuming your where conditions uniquely identify the row. See the documentation:
https://www.cloudera.com/documentation/enterprise/5-10-x/topics/impala_delete.html
Impala delete command works only for Kudu storage type. Any storage formats other than kudu are not designed for online transactions and does not offer any real-time queries and row level updates and deletes.
Related
For a project i need to to delete all data from all tables in a database,
I tried
DELETE FROM table1,table2,table3,...;
But it doesnt work. Any advice ? Thank
I would like to refer You to this related post
How do I use cascade delete with SQL Server?
as You will find there several possible solutions.
When using SQL it means that Your data is relations, which means most of the records are somehow related in the different tables and this relation is expressed with foreign keys. However when attempting to delete data which is id is related with data in another table a cascade deletion should be implemented, the other way around it is add additional boolean column named isDeleted(as example ofcourse) and just alter specific rows to true in this specific column and then filter by preferences. Hopefully I have managed somehow to provide with alternative and/or possible solution to Your problem.
Leaving also this link which gives some examples on cascade deletion and guide on how to implement it. ->
https://www.sqlshack.com/delete-cascade-and-update-cascade-in-sql-server-foreign-key/
P.S. also if You want just to DELETE all the data You can either use TRUNCATE TABLE or DROP DATABASE query. With the latest option You will have to recreate the database once more.
Because you want to delete all databases from all tables, you are essentially deleting the database.
The sqlite way of doing this is to just delete the database file.
In contrast to postgres or mongodb or most databases, sqlite doesn't have a server so no need to call DROP DATABASE.
As soon as the file is gone and you open the database from your application you will be in a blank state again.
I am trying to do a full load of a table in big query daily, as part of ETL. The target table has dummy partition column of type integer and is clustered. I want to have the statement to be atomic i.e either it will completely overwrite the new data or rollback to old data in case of failure for any reason in between and it will serve user queries with old data until it completely overwritten.
One way of doing this is delete and insert but big query does not support multi statement transactions.
I am thinking to use the below statement. Please let me know if this is atomic.
create or replace table_1 partition by dummy_int cluster dummy_column
as select col1,col2,col3 from stage_table1
I've been working on deleting all the rows in Azure table in java. Can I do it without querying it?
Thanks in advance
If I retrieve all the data, can I perform delete query on that?
If you just want to delete data, you just need to retrieve PKs and RKs. After retrieved all the data of PKs and RKs, you could perform the delete query for the entities one by one.
For complex delete query, for example, below query is not supported currently.
delete from tablename where PK = ''
I suggest you submit your idea on Azure feedback site which is used for features request.
https://feedback.azure.com/forums/217298-storage
If you don't want to query the table, what you can do is to delete the table and recreate it.
I have a table that has something like half a million rows and I'd like to remove all rows.
If I do simple delete from tbl, the transaction log fills up. I don't care about transactions this case, I do not want to rollback in any case. I could delete rows in many transactions, but are there any better ways to this?
How to efficiently remove all rows from a table in DB2? Can I disable the transactions for this command somehow or is there special commands to do this (like truncate in MySQL)?
After I have deleted the rows, I will repopulate the database with similar amount of new data.
It seems that following command works in newer versions of DB2.
TRUNCATE TABLE someschema.sometable IMMEDIATE
To truncate a table in DB2, simply write:
alter table schema.table_name activate not logged initially with empty table
From what I was able to read, this will delete the table content without doing any kind of logging which will go much easier on your server's I/O.
I am working on an in-house ETL solution, from db1 (Oracle) to db2 (Sybase). We needs to transfer data incrementally (Change Data Capture?) into db2.
I have only read access to tables, so I can't create any table or trigger in Oracle db1.
The challenge I am facing is, how to detect record deletion in Oracle?
The solution which I can think of, is by using additional standalone/embedded db (e.g. derby, h2 etc). This db contains 2 tables, namely old_data, new_data.
old_data contains primary key field from tahle of interest in Oracle.
Every time ETL process runs, new_data table will be populated with primary key field from Oracle table. After that, I will run the following sql command to get the deleted rows:
SELECT old_data.id FROM old_data WHERE old_data.id NOT IN (SELECT new_data.id FROM new_data)
I think this will be a very expensive operation when the volume of data become very large. Do you have any better idea of doing this?
Thanks.
Which edition of Oracle ? If you have Enterprise Edition, look into Oracle Streams.
You can grab the deletes out of the REDO log rather than the database itself
One approach you could take is using the Oracle flashback capability (if you're using version 9i or later):
http://forums.oracle.com/forums/thread.jspa?messageID=2608773
This will allow you to select from a prior database state.
If there may not always be deleted records, you could be more efficient by:
Storing a row count with each query iteration.
Comparing that row count to the previous row count.
If they are different, you know you have a delete and you have to compare the current set with the historical data set from flashback. If not, then don't bother and you've saved a lot of cycles.
A quick note on your solution if flashback isn't an option: I don't think your select query is a big deal - it's all those inserts to populate those side tables that will really take a lot of time. Why not just run that query against the sybase production server before doing your update?