Needed delete cascade query to delete data from 3tables at a time

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SQL-Server

hi i have 3 tables (a table,b table,c table)

in 'a' Table :- columns are akey as primarykey int, aname as varchar,

in 'b' Table :- columns are bkey as primarykey int, akey(fkey) int , address as varchar(100),

in 'c' Table :- columns are ckey as primarykey, bkey(fkey) int, city as varchar(20)

here i want to delte the data from a table, but not able to delete bcoz i'm getting below error:-

The DELETE statement conflicted with the REFERENCE constraint

for this i want to use "delete cascade query" can any one help to how use thie one with example