SQL statements deletes and adds a foreign key, a primary key method _c# tutorial

--Delete foreign keys
Syntax: ALTER TABLE name DROP constraint foreign KEY constraint name
Such as:
ALTER TABLE STU_PKFK_SC DROP constraint fk_s
ALTER TABLE STU_PKFK_SC DROP constraint Fk_c
--Adding foreign keys
Syntax: ALTER TABLE name ADD constraint foreign KEY constraint name foreign key (column name) references Reference foreign key table (column name)
Such as:
ALTER TABLE STU_PKFK_SC
Add Constraint fk_s
Foreign KEY (SNO)
References stu_pkfk_s (SNO)
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--Delete primary key
Syntax: ALTER TABLE name DROP constraint PRIMARY KEY constraint name
Such as:
ALTER TABLE stu_pkfk_s DROP constraint pk_s
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--Add primary key
Syntax: ALTER TABLE name ADD constraint PRIMARY KEY constraint name primary key (column name)
ALTER TABLE stu_pkfk_s ADD constraint pk_s primary key (SNO)
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