Why developers need to learn the basics of query optimisation. How to make the learning process easy and pleasant.
I am organising a free event with several talks from Percona experts, in London. Also, some news about events I have attended or contributed recently.
It is quite common to use an equality condition and an IS NULL condition on the same columns. Unfortunately, this could make queries very slow.
Any comparison involving at least one NULL operand will return NULL. However, SQL supports operators to easily write NULL-safe comparisons.