分割槽過濾

1. 如果不加分割槽，預設會掃描整個表的資料
2. 如何查看錶有哪些分割槽：show partitions databaseName.tableName
3. 如何確認分割槽是否生效：explain dependency sql

分割槽放置位置

1. 普通查詢，分割槽過濾放在where後面，如
   select * from table1 t1 where t1.date between '20151205' and '20151206'
   
   • 說明：var between ‘a’ and ‘b’意思是var>=’a’ and var<=’b’
2. inner join，分割槽過濾放在where後面，如
   select * from table1 t1 join table t2 on (t1.id=t2.id) where t1.date between '20151205' and '20151206' and t2.date between '20151205' and '20151206'

3. left join，左邊表的分割槽過濾放在where後面，右邊表分割槽過濾放在on後面，如
   select * from table1 t1 left join table t2 on (t1.id=t2.id and t2.date between '20151205' and '20151206') where t1.date between '20151205' and '20151206'

   
   • 說明：right join相反

除了分割槽條件的放置之外其他的條件也類似，如t2.order_type=’3’放置在where後面則是在join之後進行過濾，放在on後面則是在join之前過濾