Column Indexing and DELETE query performance

Question

I have a table with few Columns like ID (PK), Name, created_time etc. and periodically I DELETE rows from this table by using this simple DELETE query.

DELETE FROM my_table WHERE created_time < 'some time';

Just want to know what will be the performance impact on INSERT , SELECT and DELETE if I make or not make an INDEX on created_time .

This table may have millions of rows and one DELETE query may delete rows in hundred thousands in one go.

Database : Oracle, JavaDB, DB2, SQL Server

Answer 1

If you make an INDEX on created_time. 1. Insert it will slow because it need to check column created_time is one time only(like a key). 2. SELECT and DELETE will quick if your condition where WHERE created_time = 'some time' It's mean if it find the first row of condition it will stop.