Existing table, there are fields A, B, A is code, B value, one to one correspondence, when I update or insert A new B value, all values are updated under the corresponding code, for example:
A, B
1 FG
1 FG
2 FD
3 FR

Now insert a row 1 FT data, trigger automatic updates, get data:
A, B
1 FT
1 FT
2 FD
3 FR
1 FT
Consult a great god, and how to write this?