[dmach]

I think of inner & outer joins like AND & OR. An inner join will only return a result if the value of key that the join is on exists in both tables. An outer join will give rows for all key values in both tables even if values are only in one or the other table with null results in the row for the columns of the opposite table. Inner joins are the default as you are generally interested in what matches between tables but you have the option of outer if you need to get the full messy picture or if you are doing ETL and want to ensure no badish records are missing.

[isuckatcoding]

My goodness. Thank you for this explanation. I've always googled the concept and forgot about it but this sticks.