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                列處理:在 SELECT 中,只拿需要的列,如果有,盡量使用分區過濾,少用`SELECT *`。 <br/> 行處理:在分區剪裁中,當使用外關聯時,應盡量避免將副表的過濾條件寫在 `where`后面,如果這樣做就會先全表關聯,之后才能過濾。 ```sql ### 比較下面兩種查詢方式的運行時間 (1)先關聯兩張表,再用副表的where 條件過濾 hive (default)> select o.id from bigtable b join ori o on o.id = b.id where o.id <= 10; Time taken: 63.316 seconds, Fetched: 100 row(s) (2)通過子查詢后,再關聯表 hive (default)> select b.id from bigtable b join (select id from ori where id <= 10 ) o on b.id = o.id; Time taken: 61.106 seconds, Fetched: 100 row(s) ```
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