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ALTER TABLE dbo.T2
DROP CONSTRAINT FK_T1_T2 -- or whatever it's called
ALTER TABLE dbo.T2
ADD CONSTRAINT FK_T1_T2_Cascade
FOREIGN KEY (EmployeeID) REFERENCES dbo.T1(EmployeeID) ON DELETE CASCADE
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CREATE TBALE parent_table_p (
id INT PRIMARY KEY
)
CREATE_TABLE child_table_c(
id INT PRIMARY KEY,
parent_id INT,
FOREIGN KEY (parent_id) REFERENCES parent_table_p(id) ON DELETE CASCADE
)
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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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The ON DELETE CASCADE clause specifies that if a row in the
table A is deleted, any rows in the table B that reference the deleted
row will also be deleted.
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CREATE TABLE child_table
(
column1 datatype [ NULL | NOT NULL ],
column2 datatype [ NULL | NOT NULL ],
CONSTRAINT fk_name
FOREIGN KEY (child_col1, child_col2, child_col_n)
REFERENCES parent_table (parent_col1, parent_col2, parent_col_n)
ON DELETE CASCADE
[ ON UPDATE { NO ACTION | CASCADE | SET NULL | SET DEFAULT } ]
);
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CREATE TABLE Enroll (
sno INT,
cno INT,
jdate date,
PRIMARY KEY(sno,cno),
FOREIGN KEY(sno)
REFERENCES Student(sno)
ON DELETE CASCADE
FOREIGN KEY(cno)
REFERENCES Course(cno)
ON DELETE CASCADE
);