Data Types
Ref: https://docs.oracle.com/cd/A97630_01/server.920/a96524/c13datyp.htm
(Click on the image to see it properly)
Why PLS_Integer:
https://docs.oracle.com/cd/B13789_01/appdev.101/b10807/03_types.htm
“You use the PLS_INTEGER datatype to store signed integers. Its magnitude range is -231 .. 231. PLS_INTEGER values require less storage than NUMBER values. Also, PLS_INTEGER operations use machine arithmetic, so they are faster than NUMBER and BINARY_INTEGER operations, which use library arithmetic. For efficiency, use PLS_INTEGER for all calculations that fall within its magnitude range.”
ROWID vs ROWNUM
ROWID is useful when you need to refer to a specific row in a table without using a primary key or unique constraint. Hence, ROWNUM is a pseudocolumn that assigns a unique row number to each row in a result set, while ROWID is a physical address that identifies a specific row in a table
https://www.c-sharpcorner.com/interview-question/what-is-the-difference-between-rownum-and-rowed
Simple Integer vs PLS_integer
https://docs.oracle.com/en/database/oracle/oracle-database/19/lnpls/plsql-data-types.html
“SIMPLE_INTEGER has the same range as PLS_INTEGER and has a NOT NULL constraint. It differs significantly from PLS_INTEGER in its overflow semantics. If you know that a variable will never have the value NULL or need overflow checking, declare it as SIMPLE_INTEGER rather than PLS_INTEGER .”
