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ALTER TABLE TABLEName
drop CONSTRAINT FK_CONSTRAINTNAME;
ALTER TABLE TABLENAME
ADD CONSTRAINT FK_CONSTRAINTNAME
FOREIGN KEY (FId)
REFERENCES OTHERTABLE
(Id)
ON DELETE CASCADE ON UPDATE NO ACTION;
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ALTER TABLE child_table_name WITH CHECK ADD FOREIGN KEY(child_column_name)
REFERENCES parent_table_name (parent_column_name) ON DELETE CASCADE