If your SQL’s runtime is short such as less than 10 seconds, the time of data cache from hard disc to memory and SQL parsing time may be significant to the total runtime. So, execute every SQL alternative for 2 times and use the second runtime to compare with each other.
For very short time SQL statements with runtime less than 1 second, it is recommended to run all SQL alternatives multiple times such as 3 times or more to have an average runtime to compare with each other.
Alternative Wisdom