Another way to calculate summary statistics in SQL is to use the GROUP BY clause, which allows you to divide the rows in a table into groups based on one or more columns or expressions.

The error “Column is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause” occurs in SQL when a SELECT ...

The mammals database has a several thousand rows of data. But how much data does it actually have? A quick way to find out is to run our first aggregate function. Pretty much the same thing as the ...