Oracle syntax example for adding table constraints

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Example:

--Class table

CREATE TABLE   number VARCHAR2 (not NULL);

--Add a primary key to the Tclass table

ALTER TABLE ADD CONSTRAINT  PRIMARYKEY(cl_id);

---student table

CREATE TABLESTUDENT (st_idVARCHAR2( -),--Single-line comment primary keySt_codeVARCHAR2( -),--UNIQUE ConstraintSt_nameVARCHAR2( -),--non-null constraintSt_age Number, St_birthday DATE,--Default ConstraintsSt_sexVARCHAR2(4),--Add a Check constraintcl_id Number            --Add a foreign key (the primary key of the primary table is referenced));

--Add primary key to student table

ALTER TABLE ADD CONSTRAINT PRIMARY KEY (st_id);

--Give Name list non-empty constraint

ALTER TABLE  CONSTRAINTnotNULL;

--Add a unique constraint to St_code

　　

ALTER TABLE ADD CONSTRAINT UNIQUE (St_code);

　　

--st_sex can only be male or female

ALTER TABLE ADD CONSTRAINT CHECK (St_sex=' male 'OR st_sex=' female ' );

--st_birthday Default to Sysdate

ALTER TABLE DEFAULT Sysdate;

---adding foreign keys

ALTER TABLE ADD CONSTRAINT FOREIGN KEY REFERENCES Tclass (cl_id);

Oracle syntax example for adding table constraints