When trying to add data from same table

AFINumber	AFIAmount	OriginalAFINumber	OriginalAFIAmount
2024MSVMX00574-OV1	0.00	2024MSVMX00574	NULL
2024MSVMX00575-OV2	0.00	2024MSVMX00575	NULL
2025HSCIN041092-OV4	1111.00	2025HSCIN041092	NULL

Select T.OriginalAFINumber,T.AFIAmount,T.AFINumber,t.OriginalAFIAmount,O.AFINumber,O.AFIAmount

update T

SET T.OriginalAFIAmount = O.AFIAmount

FROM tbl_afiOverrunAmount_dlt T

INNER JOIN tbl_AFIDetails O 

    ON T.OriginalAFINumber = O.AFINumber

WHERE T.OriginalAFIAmount IS NULL;