Hi all. Maybe mine is a stupid question, but I'd like to know the answer if possible. In an inner join involving a 16M+ rows table and a 100+ rows table performances got drastically improved by 100+ times by replacing a UNIQUE-NOT NULL index with a PRIMARY KEY on the very same columns in the very same order. The query has not been modified. In the older case, thanks to the EXPLAIN command, I saw that the join was causing a sort on the index elements, while the primary key was not. So ther's some difference for sure, but I'm missing it. Any hint? -- Vincenzo Romano -= NotOrAnd.IT Information Technologies =- tel +39 0823 454163 | cel +39 339 8083886 | fax +39 02 700506964 <Smooth seas never make experienced sailormen>
