mysql - mysql中三个表的内连接花费太长时间

Question

我正在查询 mysql 中的 3 个表。

SELECT t1.some_col
,t2.some_col
,t3.some_col

FROM t1, t2, t3
WHERE t1.a_col = t2.a_col AND t2.a_col = t3.a_col
AND a filter on t1
AND a filter on t2
AND a filter on t3

这花费了太多时间。 (10 分钟后甚至没有给出结果)。任何优化建议都会很棒。

表 t1(0.3m 行)、t2(1.1m)和 t3(258 行)。没有表有索引，即使我也不允许创建索引。

编辑(顺便说一句，嗯？):

SELECT t2.parent_customerID ,
aggregate(t1.some_columns) 
FROM t1, t2, t3 
WHERE t1.customerID = t2.customerID 
AND t2.parent_customerID = t3.parent_customerID 

AND t1_where_entity_type_customer 
AND t2_parent_customer_belonging_a_region_filter 
AND t3_a_flag_check_on_parent_customer 
GROUP BY t2.parent_customer

Answer 1

尝试这种方法。

SELECT t1.some_col
,t2.some_col
,t3.some_col
FROM t1 
INNER JOIN t2 ON t1.a_col = t2.a_col
INNER JOIN t3 ON t2.a_col = t3.a_col
WHERE a filter on t1 AND a filter on t2 AND a filter on t3