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  1. #1
    Join Date
    Mar 2010
    Posts
    3

    Unanswered: What exactly are constraints

    I have the following example and am trying to understand what Constraints are doing. This is the code:

    Code:
    CREATE TABLE donation
    (	donation_id 	NUMBER 
    			CONSTRAINT donation_id_pk PRIMARY KEY,
    	donator 	NUMBER
    			CONSTRAINT donation_donator_nn NOT NULL
    			CONSTRAINT donation_donator_fk REFERENCES person(id),
    	type 		CHAR(1) 
    			DEFAULT 'C'
    			CONSTRAINT donation_type_cc CHECK(type IN('C','M','V'))
    			CONSTRAINT donation_type_nn NOT NULL,
    	amount 		NUMBER(8,2)
    			CONSTRAINT donation_amount_cc CHECK (amount > 0 AND amount <= 100),
    	dateDonate 	DATE,
    	note 		VARCHAR2(80));
    From what I understand the constraint enforces a rule? So to check and make sure a value is not null or a value is in a certain range?

    Thanks

  2. #2
    Join Date
    Mar 2006
    Posts
    53
    Or is a value that actually exists in another table (foreign key constraint).
    Now back on Oracle. The more things change, the more they stay the same.

  3. #3
    Join Date
    Aug 2003
    Location
    Where the Surf Meets the Turf @Del Mar, CA
    Posts
    7,776
    Provided Answers: 1
    When all else fails, Read The Fine Manual

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