By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
| serial_number | substring_index(serial_number, '_', 1) |
|---|---|
| 8009914407 | 8009914407 |
| MCO | MCO |
| 8558201722 | 8558201722 |
| US2 | US2 |
| US3 | US3 |
| MCO | MCO |
| 7272950703 | 7272950703 |
| US2 | US2 |
| MCO | MCO |
| null | null |
| 8558201722 | 8558201722 |
| 7272505721_R2C | 7272505721 |
| 8002094684 | 8002094684 |
| 8558088363_AAC | 8558088363 |
| null | null |
| US2 | US2 |