How to select the unique values in one column and group by a different column

I have a table in Oracle that has a schema as shown below

Copy tables and fields by variables

I need to copy some selected records from multiple tables.
To determine the records to copy, I would use MINUS of two SELECTs like this:

Performance tuning of Update statement in ORACLE

I have this code, and it is taking 8 to 9 hours for 450k rows of data to complete. How to improve performance in that case? tab_a has 10M of data.

Getting error ORA-29273 – “HTTP request failed” when tried to make an utl_http.request in oracle sql developer

Here is what I’m trying to do:

Getting error ORA-29273 – “HTTP request failed” when tried to make an utl_http.request in oracle sql developer

Here is what I’m trying to do:

Getting error ORA-29273 – “HTTP request failed” when tried to make an utl_http.request in oracle sql developer

Here is what I’m trying to do:

Getting error ORA-29273 – “HTTP request failed” when tried to make an utl_http.request in oracle sql developer

Here is what I’m trying to do:

Getting error ORA-29273 – “HTTP request failed” when tried to make an utl_http.request in oracle sql developer

Here is what I’m trying to do:

Calling Oracle LISTAGG function from a Function

I have written the following Oracle PL/SQL Function that calls the LISTAGG function

Anon PL/SQL block to test FUNCTION with return of REF CURSOR and OUTPUT variable

I have a FUNCTION inside a PACKAGE which ALSO has an OUTPUT variable