SQL查詢替代爲LEFT OUTER /優化JOIN

Question

我有以下查詢：

SELECT 
    `pokemon_moves`.`pokemon_move_method_id`, 
    `pokemon_moves`.`level`, 
    `move`.`id`, 
    `move`.`name` 
FROM 
    `pokemon_moves` 
LEFT OUTER JOIN 
    `moves` `move` ON 
     `move`.`id` = `pokemon_moves`.`move_id` 
WHERE 
    `pokemon_moves`.`pokemon_move_method_id` < '4' AND 
    `pokemon_moves`.`pokemon_id` = '2' AND 
    `pokemon_moves`.`version_group_id` = '6' 
ORDER BY 
    CAST(`pokemon_moves`.`level` as INTEGER) ASC, 
    `move`.`name` ASC 

這是有點慢，我想那是因爲moves查詢表在pokemon_moves表的每一行，而不是隻符合WHERE條款的。寫這個查詢有什麼更好的選擇？

請注意，在這個（外部）表中的整數被存儲爲文本

Answer 1

嘗試使用內部連接，並把你的WHERE條件到JOIN語句。例如：

SELECT 
    `pokemon_moves`.`pokemon_move_method_id`, 
    `pokemon_moves`.`level`, 
    `move`.`id`, 
    `move`.`name` 
FROM 
    `pokemon_moves` 
INNER JOIN 
    `moves` `move` ON 
    `pokemon_moves`.`pokemon_id` = '2' AND 
    `pokemon_moves`.`version_group_id` = '6' AND 
    `pokemon_moves`.`pokemon_move_method_id` < '4' AND 
    `move`.`id` = `pokemon_moves`.`move_id` 
ORDER BY 
    CAST(`pokemon_moves`.`level` as INTEGER) ASC, 
    `move`.`name` ASC