Using Defined Variables in MySQL (example)

It's been a long time coming, but I've finally learnt how to make use of variables in MySQL.

In my example, I wanted to find the maximum tk, and then use that maximum tk to display tk and fullDate (for that maximum tk.) Here is how I did it:

mysql> SET @var = (SELECT max(tk) FROM dwh_capacity_efficiency.date_dimension);

mysql> SELECT tk,fullDate FROM dwh_capacity_efficiency.date_dimension where tk = @var;

+-----+---------------------+

| tk  | fullDate            |

+-----+---------------------+

| 358 | 2017-05-08 00:00:00 |

+-----+---------------------+

Image: Example of how to use a variable in MySQL