mysql - MySQL 上 NOT IN 的替代方案

Question

我有一个查询

SELECT DISTINCT phoneNum 
FROM `Transaction_Register` 
WHERE phoneNum NOT IN (SELECT phoneNum FROM `Subscription`) 
LIMIT 0 , 1000000

执行 b/c 表需要太多时间，Transaction_Register有数百万条记录是否有上述查询的替代方法，如果有的话，我将不胜感激。

Answer 1

另一种方法是使用 LEFT JOIN：

select distinct t.phoneNum
from Transaction_Register t
left join Subscription s
  on t.phoneNum = s.phoneNum
where s.phoneNum is null
LIMIT 0 , 1000000;

请参阅带有演示的 SQL Fiddle

Answer 2

我怀疑是否LEFT JOIN真的表现得比NOT IN. 我只是用下面的表结构进行了一些测试（如果我错了请纠正我）：

account (id, ....)   [42,884 rows, index by id]
play (account_id, playdate, ...)   [61,737 rows, index by account_id]

(1) 查询LEFT JOIN

SELECT * FROM
account LEFT JOIN play ON account.id = play.account_id
WHERE play.account_id IS NULL

(2) 查询NOT IN

SELECT * FROM
account WHERE
account.id NOT IN (SELECT play.account_id FROM play)

使用 LIMIT 0 进行速度测试，...

LIMIT 0,->   100      150      200      250
-------------------------------------------------------------------------
LEFT         3.213s   4.477s   5.881s   7.472s
NOT EXIST    2.200s   3.261s   4.320s   5.647s
--------------------------------------------------------------------------
Difference   1.013s   1.216s   1.560s   1.825s

随着我增加限制，差异越来越大

---

和EXPLAIN

(1) 查询LEFT JOIN

SELECT_TYPE   TABLE      TYPE   ROWS    EXTRA
-------------------------------------------------
SIMPLE         account   ALL    42,884
SIMPLE         play      ALL    61,737  Using where; not exists

(2) 查询NOT IN

SELECT_TYPE          TABLE      TYPE   ROWS   EXTRA
-------------------------------------------------
SIMPLE               account   ALL    42,884  Using where
DEPENDENT SUBQUERY   play      INDEX  61,737  Using where; Using index

似乎 LEFT JOIN 没有使用索引

逻辑

(1) 查询LEFT JOIN

帐户和游戏之间的 LEFT JOIN 后将产生 42,884 * 61,737 = 2,647,529,508 行。然后检查这些行上的 play.account_id 是否为 NULL。

(2) 查询NOT IN

二进制搜索以 log2(N) 为项目存在。这意味着 42,884 * log2(61,737) = 686,144 步