There are two fields A in the data table class, field B
All of the fields in field A contain data, and some of the fields in field B contain data and some are NULL
Such as
A B
10 2
15 7
9 Null
16 8
7 Null
11 Null
How to make field B equal to the data of field A if it is NULL
That is to achieve the following effect
A B
10 2
15 7
9 9
16 8
7 7
11 11
