Oracle SQL左侧和右侧外部联接，带/不带where子句，提供不同的输出

为什么以下查询的输出有差异

根据我的理解，它应该为前3个查询提供相同的输出，并为后3个查询提供相同的输出

select count(*) 
from CTM_People a left outer join user_x b 
     on a.remedy_login_id = b.login_name;

结果1:152771

select count(*) 
from CTM_People a left outer join user_x b 
     on a.remedy_login_id = b.login_name 
where a.remedy_login_id like '%';

select count(*) 
from CTM_People a right outer join user_x b 
     on a.remedy_login_id = b.login_name;

结果2:151185

select count(*) 
from CTM_People a left outer join user_x b 
     on a.remedy_login_id = b.login_name and a.remedy_login_id like '%';

结果3:152771

select count(*) 
from CTM_People a left outer join user_x b 
     on a.remedy_login_id = b.login_name 
where a.remedy_login_id like '%';

select count(*) 
from CTM_People a right outer join user_x b 
     on a.remedy_login_id = b.login_name;

结果1:150899

select count(*) 
from CTM_People a right outer join user_x b 
     on a.remedy_login_id = b.login_name where a.remedy_login_id like '%';

select count(*) 
from CTM_People a right outer join user_x b 
     on a.remedy_login_id = b.login_name and a.remedy_login_id like '%';

结果2:150889

select count(*) 
from CTM_People a right outer join user_x b 
     on a.remedy_login_id = b.login_name where a.remedy_login_id like '%';

select count(*) 
from CTM_People a right outer join user_x b 
     on a.remedy_login_id = b.login_name and a.remedy_login_id like '%';

结果3:150899

select count(*) 
from CTM_People a right outer join user_x b 
     on a.remedy_login_id = b.login_name where a.remedy_login_id like '%';

select count(*) 
from CTM_People a right outer join user_x b 
     on a.remedy_login_id = b.login_name and a.remedy_login_id like '%';

两个表中的总计数均为

select count(*) from CTM_People; **Result : 152771**
select count(*) from user_x; **Result : 150899**

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LIKE运算符不接受空值。请检查a.rememy\u login\u id

LIKE运算符不接受空值。在.remedy\u login\u id中是否有空值？如果您使用的是Oracle，请调整您的标记并删除MySQL和SQL Server。可能有提到的@DavidP之类的空值，第三个不受影响，因为“%”是外部联接条件，另一个区别取决于外部联接的表。谢谢David和James。我得到了它。CTM_People表实际上有1586个空值。我添加了我以前的注释作为答案，这样你们就可以接受或者其他什么了。