What's the difference between a primary key and a unique key?
Answer Posted / sunil
HI ALL
IN CASE OF INSERTING REPETED NULL IN UNIQUE KEY COLOUMN ,
IF IT IS COMPOSITE KEY IS POSSIBLE. . . ANY LOGICAL RESON?
Eg:
CREATE TABLE TRY(ROLL NUMBER,LIB_CARD_NO NUMBER,
CONSTRAINT CON_UNQ UNIQUE(ROLL,LIB_CARD_NO));
INSERT INTO TRY VALUES(NULL,NULL);
--> 1 ROW CREATED
INSERT INTO TRY VALUES(NULL,NULL);
--> 1 ROW CREATED -- REPETED NULL ARE ALLOWED!!!!
| Is This Answer Correct ? | 2 Yes | 0 No |
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