T E Schmitz wrote:
> The following self join of a table containing 5800 records is crawling:
>
> SELECT
> history.stock, history.day, history.high, history.low,
> MAX(past_week.high) AS week_high,
> MAX(past_month.high) AS month_high
> FROM history
> INNER JOIN history AS past_month ON (past_month.stock = history.stock
> AND past_month.day < history.day AND past_month.day >= (history.day - 30))
> INNER JOIN history AS past_week ON (past_week.stock =
> past_month.stock AND past_week.day < history.day AND past_week.day >=
> (history.day - 7))
> GROUP BY history.stock, history.day, history.high, history.low
> ORDER BY history.stock, history.day DESC
Things improved hugely when I changed the JOIN clauses:
LEFT OUTER JOIN history AS past_month ON (past_month.stock =
history.stock AND past_month.day >= (history.day - 30) AND
past_month.day < history.day)
LEFT OUTER JOIN history AS past_week ON (past_week.stock =
past_month.stock AND past_week.day =past_month.day AND past_week.day >= (history.day - 7))
--
Regards,
Tarlika Elisabeth Schmitz
