Join types

If you’re not sure which join to use to merge your queries, here are brief descriptions and illustrations for each available join type:

Outer join

Combines the columns from all result sets on one or more common columns when possible, and includes all data from both result sets

You can also select whether or not to include NULL match rows.

Inner join

Combines the columns on a common column (one or more leftmost columns) when possible, and only includes data for the columns that share the same values in the common columns.

Left join

Combines the columns on a common column (one or more leftmost columns) when possible, returning all rows from the first result set with the matching rows in the second result set. The result is null in the second result set when there is no match.

Union

Stacks the result sets on top of each other without grouping or combining the data. Use unions to generate tabular lists of data for printing or viewing.

To remove duplicate rows, select the Distinct checkbox.

If you select to include query names, this adds an extra column titled Layer to your result set. It labels each row with name of the query that it came from.

Cross join

Results in a table with all possible combinations of your result sets together. This can result in enormous tables, so use a cross join with caution. For example, only use it when your result sets return single values.