Search for a table in B tables no data records how to write SQL statements

How to write SQL statements when searching for a record with no data in table B?
Such as:
Table A
a_id name .....
1 sheets of three
2 John Doe
3 Harry
4 Zhao Liu


b table
b_id a_id Total
1 1 100
2 3 200


Check the above arrears after submission how to search out John Doe and Zhao Liu????
------Solution--------------------
It is not necessary to show that Harry is paying for it and is not being wasted.
The owner should be looking for a customer who is not paying or has

Select T1.name from a as T1 left join B as T2 on t1.a_id=t2.a_id where Qianfei is null or qianfei>0;

You can write this, left join first, and then find qianfei>0 or Qianfei as null.

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