Creating Index

Hi all,

I am wonderring the differences between creating an index on several columns
of a table and an index on each column of a table.

For example, following is my select query:

select * from my_table where myrowid='abc' and mytask='TEst 1' and
myday!='holiday';

Which of the following is a correct way of indexing the column?

1. create index my_table_my_index on my_table(myrowid, mytask, myday);
2. i. create index my_table_myrow_index on my_table(myrowid);
ii. create index my_table_mytask_index on my_table(mytask);
iii. create index my_table_myday_index on my_table(myday);

All helps are appreciated.

THanks.

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