Re: Optimize Inner Join With WHERE BETWEEN dates

[Rick James]

AND a.ClockIn <> b.ClockOut
AND a.ClockOut <> b.ClockIn
AND ( a.ClockIn BETWEEN b.ClockIn AND b.ClockOut
OR a.ClockOut BETWEEN b.ClockIn AND b.ClockOut
)
-->
AND a.ClockIn < b.ClockOut AND a.ClockOut > b.ClockIn

That is much simpler than what you have, but, alas, may not be faster.
There is no simple way to optimize overlapping ranges.

Need to see SHOW CREATE TABLE.
SHOW VARIABLES LIKE '%buffer%';

rows: 3766 -- discouraging
Extra: Using where; Using index -- encouraging

rows: 82 -- discouraging
Extra: Using where; Using index -- encouraging

key_len: 5 -- Are the fields NULLable? Shouldn't they be NOT NULL?