How to use index in select statement?

Question

Lets say in the employee table, I have created an index(idx_name) on the emp_name column of the table.

Do I need to explicitly specify the index name in

Answer 1

How to use index in select statement?
this way:

   SELECT * FROM table1 USE INDEX (col1_index,col2_index)
    WHERE col1=1 AND col2=2 AND col3=3;

SELECT * FROM table1 IGNORE INDEX (col3_index)
WHERE col1=1 AND col2=2 AND col3=3;

SELECT * FROM t1 USE INDEX (i1) IGNORE INDEX (i2) USE INDEX (i2);

And many more ways check this

Do I need to explicitly specify?

• No, no Need to specify explicitly.
• DB engine should automatically select the index to use based on query execution plans it builds from @Tudor Constantin answer.
• The optimiser will judge if the use of your index will make your query run faster, and if it is, it will use the index. from @niktrl answer