hw3_hfan - (2) Answer and submit your answers to the...

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(2) Answer and submit your answers to the following questions a) . a. The primary key is the identifier field or attribute that uniquely identifies a record (Rainer and Turban, “Information system”, p.109). The Foreign Key is a referential constraint between two tables.[1] The foreign key identifies a column or a set of columns in one (referencing) table that refers to a column or set of columns in another (referenced) table ( http://en.wikipedia.org/wiki/Foreign_key ). b. An inner join requires each record in the two joined tables to have a matching record. An inner join essentially combines the records from two tables (A and B) based on a given join-predicate. A full outer join combines the results of both left and right outer joins. The joined table will contain all records from both tables, and fill in NULLs for missing matches on either side. A right outer join (or right join) closely resembles a left outer join, except with the tables reversed. Every record from the "right" table (B) will appear in the joined table at least once. If no matching row from the "left" table (A) exists, NULL will appear in columns from
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This note was uploaded on 05/06/2010 for the course IE 332 taught by Professor Jisoo during the Spring '10 term at Punjab Engineering College.

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hw3_hfan - (2) Answer and submit your answers to the...

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