Transcription of Displaying Data from Multiple Tables
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Displaying Data from Multiple Tables
Displaying data fromMultiple TablesChapter 41 ObjectivesAfter completing this lesson, you should be able to do the following: Write SELECT statements to accessdata from more than one table usingequality and nonequality joins View data that generally does not meet ajoin condition by using outer joins Join a table to itselfLesson AimThis lesson covers how to obtain data from more than one table , using the different methods product A Cartesian product is formed when: A join condition is omitted A join condition is invalid All rows in the first table are joined to all rows in the second tableTo avoid a Cartesian product , always include a valid join condition in aWHERE a Cartesian ProductSELECT ename, dnameFROM emp, dept;ENAME DNAME BLAKE ACCOUNTING SMITH ACCOUNTING ALLEN ACCOUNTING 56 Rows Selected4 What Is a Jo
Cartesian Product • A Cartesian product is formed when: • A join condition is omitted • A join condition is invalid • All rows in the first table are joined to all rows in the second table To avoid a Cartesian product, always include a valid join condition in a
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