tbl_1:
key  col1 col2
---  ---- ----
1    abc  123
2    xyz  987

tbl_2:
key  col3 col4
---  ---- ----
1    bcd  12.5
2    zzz  11.1

tbl_3:
key  col1 col2 col3 col4
---  ---- ---- ---- ----
1    abc  123  bcd  12.5
2    xyz  987  zzz  11.1