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There are three colours (red, green, and blue). You do this with the keyword distinct.įor example, you can find the number of different values in the colour column by passing "distinct colour" to count. But most allow you to work on the unique values in the input. You can find a complete list of aggregate functions in the docs.īy default aggregate functions use every input value. There are also many other, more specialized aggregates. The following query shows these in action: select sum ( weight ), min ( weight ), max ( weight ),

Variance: the statistical variance of the values.Median: the middle value in the data set.Avg: the arithmetic mean of all the values in the group.Sum: the result of adding up all the values for the expression in the group.Oracle Database includes many statistical aggregate functions. For example, the following shows you how many rows where colour is not null: select count ( colour ) from bricks Īll other (non-count) aggregates use an expression. This returns the number of non-null rows for the expression. You can also pass an expression (column) to it. This means return the total number of rows. So this query gets one row, showing you how many rows there are in the bricks table: select count (*) from bricks Ĭount is unusual for accepting *. So the query will return one row.įor example, count() returns the number of rows the query processed. If you use these without group by, you have one group. The query returns one row for each group. Aggregate functions combine many rows into one.