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Asked by Rekha Last Modified
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Primary key is the field of a table in which you can have only unique values and null values are not allowed. In one table you can have only one primary key or else if you want to have more than one primary key then you can create composite (BUT ONE ONLY) primary key.
Whereas Foreign key is a reference key from another table which values reside only from the field of the referenced table.
In short primary key is a master key, and you can have one primary key in one table.
And foreign key is a child reference key and you can have multiple foreign keys in one table
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foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table or the same table. In simpler words, the foreign key is defined in a second table, but it refers to the primary key or a unique key in the first table.
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read lessPrimary Key: A primary key is a field or combination of fields that uniquely identify a record in a table, so that an individual record can be located without confusion.
Foreign Key: A foreign key (sometimes called a referencing key) is a key used to link two tables together. Typically you take the primary key field from one table and insert it into the other table where it becomes a foreign key (it remains a primary key in the original table).
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