Is it good if the table has one index and a composite index in one field?

Question

CREATE TABLE test (
id INT NOT NULL,
last_name CHAR(30) NOT NULL,
first_name CHAR(30) NOT NULL,
PRIMARY KEY (id),
KEY `first_name` (first_name),
KEY `last_name` (last_name),
KEY `last_first` (last_name,first_name)
);

Is it good if the table has one index and a composite index in one field, if I have queries like:

SELECT * FROM test WHERE first_name = 'A';
SELECT * FROM test WHERE last_name= 'A';
SELECT * FROM test WHERE last_name= 'A' AND first_name = 'A';

Answer 1

tl; dr Answer: Check it out. The answer largely depends on your data and your requests, so we can not give a final answer that is suitable for all scenarios. Until you have tested it, do not use the optional composite index. It smells of premature optimization.

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