What is the use of primary key?

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What are properties of the transaction?

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IN A TABLE HAVE ONE COLUMN PRIMARY KEY..IT WILL NOT ALLOWS NULL VALUES AND DUPLICATE VALUES..INSTEAD OF PRIMARY KEY WHY CANT WE USE UNIQUE AND NOT NULL.THESE TWO ALSO DOESNT ACCEPT NULL VALUES IN NOT NULL AND UNIQUE DOESNT ACCEPT DUPLICATE VALUES? SO WHAT IS THE DIFEERENCE BETWEEN(UNIQUE,NOT NULL) AND PRIMARY KEY??????

8 Answers   rsystems,

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Can there be 2 primary keys in a table?

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What is Raise_application_error ?

1 Answers  

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what is the difference between delete and truncate statement in sql? : Sql dba

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What is difference between function and trigger?

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What is sqlcontext?

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What is Data Concarency and Consistency?

1 Answers  

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How many postgresql users are there, worldwide?

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What are its different types of dbms?

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Suppose There is a string A.B....C.......D.........E........F In this string dots (.) are not having fixed count in between of string. I want the output to have string with one dot between. I.e. A.B.C.D.E.F

6 Answers   IBM,

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