Getting Started › Left Outer Joins › Order of Predicate Evaluation › Order of Joins

Order of Joins

The join order is set when LEFT OUTER or INNER is used, otherwise the SQL optimizer determines join order (unless plan option OPT=M is used). Care must therefore be taken to ensure efficient evaluation. (This means INNER JOIN can be used in place of OPT=M to manually specify join order at the query level.)

LEFT joins always use the nested loop join method.