Update ch08: 秋招秘籍 C.md
This commit is contained in:
@@ -72,13 +72,16 @@ INSERT INTO t_act_records VALUES('u1004', 20210105);
|
||||
# 练习四:hive 数据倾斜的产生原因及优化策略?
|
||||
|
||||
|
||||
# 练习五:假设 A表有5行(关联列 name 有2行为空),B表有6行(关联列 name 有3行为空)那么 A left join B on A.name = B.name 会返回多少行结果?
|
||||
# 练习五:left join 是否会出现多出的行?
|
||||
假设 A表有5行(关联列 name 有2行为空),B表有6行(关联列 name 有3行为空)那么 A left join B on A.name = B.name 会返回多少行结果?
|
||||
|
||||
可以参考下图
|
||||
A表
|
||||
[]()
|
||||
|
||||
[A表](./img/Question_C/C05A.jpg)
|
||||
|
||||
B表
|
||||
[]()
|
||||
[B表](./img/Question_C/C05B.jpg)
|
||||
|
||||
|
||||
|
||||
|
||||
Reference in New Issue
Block a user