An SQL join clause combines records from two or more tables in a database. It creates a set that can be saved as a table or used as is. A
JOIN is a means for combining fields from two tables by using values common to each. ANSI standard SQL specifies four types of JOIN: INNER,OUTER, LEFT, and RIGHT. As a special case, a table (base table, view, or joined table) can JOIN to itself in a self-join.A programmer writes a
JOIN predicate to identify the records for joining. If the evaluated predicate is true, the combined record is then produced in the expected format, a record set or a temporary table.For More: .http://en.wikipedia.org/wiki/Join_%28SQL%29
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