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What is a “primary key”?
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What is a “primary key”?
2,478 Views | (11 votes, avg: 3.64)
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A PRIMARY INDEX or PRIMARY KEY is something which comes mainly from
database theory. From its behaviour is almost the same as an UNIQUE
INDEX, i.e. there may only be one of each value in this column. If you
call such an INDEX PRIMARY instead of UNIQUE, you say something about
your table design, which I am not able to explain in few words.
Primary Key is a type of a constraint enforcing uniqueness and data integrity for each row of a table. All columns participating in a primary key constraint must possess the NOT NULL property.
PRIMARY KEY is a unique column in the table that identifies each row. there cannot be more than 1 row in the table with the same primary key.
Primary key is a that attribute in a table which identified uniquly in the whole table.that means in this there is no repetion of data.
Primary key is unique value in the table but not
possible for null values
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