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 Join?Use a join to query data from more than one SyntaxWrite the join condition in the WHERE , table2.
What Is an Equijoin? Equijoins To determine the name of an employee’s department, you compare the value in the DEPTNO column in the EMP table with the DEPTNO values in the DEPT
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