method request for big data

Hello, I’m trying to compile some data but haven’t been able to. I’d appreciate any help or suggestions on methods.

I have three tables. The first table has 4,000 entries, and the other two tables have 1 million entries each.

1.

A B C

1.

Kin Lin Hin Pin T_in A B C

1.

Kout Lout H_out A B C

Here’s what I want to do. If the A and B values in the table match the A and B values in the second table, then take the Kin = Kout, Lin = Lout, and Hin = Hout data from the second and third tables and add the matching rows to a single table.

Then, take the A and B values from the third table and search for them again in the second table. Take the matching data where Kin = Kout, Lin = Lout, and Hin = Hout, and add them to the bottom of the table created earlier.

I want to repeat this process 20 times. I did it as shown in the image, but it wasn’t very efficient. It works, but I’m not sure about its accuracy.