If you are using table partitioning, you have likely heard of the ALTER TABLE … EXCHANGE PARTITION … WITH TABLE … command. It existed in MariaDB since forever. But if you check the manual (any manual) or search the web, you will see that almost the only use case of it is converting a partition to a standalone non-partitoned table, or converting a standalone non-partitoned table into a partition.
And the usage was designed back then to be anything but obvious. To convert a partition to a table you need first to create an empty table with the same structure as a partition, then you exchange it with a partition, and then you drop the empty partition.
Sometimes there is a need to combine data from different columns into one string. For example,
SELECT CONCAT(first_name, ‘ ‘, last_name) FROM employees;
This doesn’t look too bad, but can quickly get out of hand, if you need to do something more complex than that. For example, let’s say, we also need to mention the salary here:
SELECT CONCAT(first_name, ‘ ‘, last_name, ‘ -‘, CAST(FORMAT(salary, 0) AS VARCHAR(10)), ‘ ‘, currency) FROM employees;