sql優化對於數據庫菜鳥級的我來說一直是個非常神祕的領域,最近工作中就碰到一個簡單的sql優化問題,經過數據庫大神的改造,讓我對sql優化有了新的認識
這是我之前自己寫的查詢:
select *
from ta
where ta.name in (select tb.name
from tb
where tb.id='46XXXXXXX9'
and tb.name = '阿X'
and tb.date = '2017-02-09'
)
and ta.date = '2017-02-09';
大神改造後:
select ta.*
from ta
join tb
on ta.name = tb.name
and ta.date = tb.date
and tb.id = '46XXXXXXX9'
and tb.name = '阿X'
where ta.date = '2017-02-09';
改造後的代碼更加適合大數據量的查詢,由此認識到一點,多加練習orcl常用字,才能在實際應用時選擇