Repeated data issues in Multi-table left join

Recently, I was working on a report, which is complicated. It is generally a primary table A, A subtable B, A subtable C, and a subtable D, which counts the data corresponding to the three primary tables. At first, I directly joined the table using left join, and the result statistics were big,

The results show that there are duplicates of data. When left join is associated, if there are two U and two C instances, the data of B will be duplicated, so that there will be more data, d. If yes, there are many duplicates in the data.

Solution:

This function is intended to be implemented in an SQL statement, but it is difficult to duplicate data, and it cannot be solved by using distinct. In the end, it can only be done by word query,

For example:

Select (select sum (A. Num) from B, A where a. ID = B. ID) C, sum (A. Num) from