Using NEW_VALUE to Record Start/End Time in Oracle SQL Script

In a SQL script, I need to record the start and end time of a block which performs some DMLs, then I will query the records being DML'ed during the peroid.

COLUMN CHAR_SYSDATE NEW_VALUE START_DATETIME
SELECT TO_CHAR(SYSDATE,'YYYYMMDDHH24MISS') CHAR_SYSDATE FROM DUAL;

......
...The block
......

COLUMN CHAR_SYSDATE NEW_VALUE END_DATETIME
SELECT TO_CHAR(SYSDATE,'YYYYMMDDHH24MISS') CHAR_SYSDATE FROM DUAL;
 
SELECT ... FROM ...
 WHERE audit_creation_date BETWEEN TO_DATE('&START_DATETIME','YYYYMMDDHH24MISS') AND TO_DATE('&END_DATETIME','YYYYMMDDHH24MISS');

Indexes on Foreign Keys

Indexes on foreign keys are not always required. But I recommend to create the indexes on foreign keys when: 1) There are deletions on the parent table and 2) the child table is large.

It has happened to me a few times when deleting from the parent table, it was kind of hanging even there were no associated records in the child table. And when looking at the execution plan, it wouldn't show anything about the foreign key validation to the child table. After adding the indexes the deletions finished instantly.