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# sql06 - 6 Subqueries Objectives After completing this...

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6 6 Subqueries

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6-2 Objectives After completing this lesson, you should After completing this lesson, you should be able to do the following: be able to do the following: Describe the types of problems that subqueries can solve Define subqueries List the types of subqueries Write single-row and multiple-row subqueries
6-3 Using a Subquery to Solve a Problem Who has a salary greater than Jones’s?” Who has a salary greater than Jones’s?” “Which employees have a salary greater than Jones’s salary?” Main Query ? ? “What is Jones’s salary?” ? ? Subquery

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6-4 Subqueries The subquery (inner query) executes once before the main query. The result of the subquery is used by the main query (outer query). SELECT select_list FROM table WHERE expr operator (SELECT select_list FROM table );
6-5 2975 SQL> SELECT ename 2 FROM emp 3 WHERE sal > 4 (SELECT sal 5 FROM emp 6 WHERE empno=7566); Using a Subquery ENAME ---------- KING FORD SCOTT

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6-6 Guidelines for Using Subqueries Enclose subqueries in parentheses. Place subqueries on the right side of the comparison operator. Do not add an ORDER BY clause to a subquery.
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sql06 - 6 Subqueries Objectives After completing this...

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