update statement with self subquery in SQL

Below is the example of update statement with self subquery in SQL.

UPDATE TB1 A SET A.IND = 'N', A.ENDDT = (Select Max(C.enqDT) -1 from TB1 C where A.Bus_KEY = C.BusKEY and C.IND ='Y' group by C.BusKEY)
Where A.IND = 'Y' and A.EFFDT < (Select max(enqDT) From TB1 B Where B.col1 = A.col1 and B.bus_KEY = A.busKEY and B.IND = 'Y');