Most tables are created with a unique, progressive ID. But how to create an ID whose values are unique across multiple tables? For example, if value 1 is in table A, it must not be in table B.
Find invalid emails
How to select invalid email addresses from a column. How to reject attempts to insert invalid emails into a column.
MariaDB: Select the Fibonacci series
How to select the first N numbers from the Fibonacci series, or the Nth number from the series. This is done by using the SEQUENCE storage engine and user variables.
Aggregate a column data
How to get statistical data from a column in standard SQL. In particular it shows how to get the minimum, maximum, average values, and the standard deviation.
Find values (not) in a given range
How to use the special SQL syntax to select rows with values in a given range, or outside of it. How to deal with bounds in a reversed order.
Count a table rows
How to count a table rows, a table distinct rows, a column values, missing values, etc.