Les02 Restricting And Sorting Data

ObjectivesAfter completing this lesson, you should be able to do the following:Limit the rows retrieved by a querySort the rows retrieved by a query

Limiting Rows Using a SelectionEMP EMPNO ENAME JOB ... DEPTNO 7839KINGPRESIDENT107698BLAKEMANAGER307782CLARKMANAGER107566JONESMANAGER20 ..."…retrieve allemployeesin department 10"EMP EMPNO ENAME JOB ... DEPTNO 7839KINGPRESIDENT107782CLARKMANAGER107934MILLERCLERK10

Limiting Rows SelectedRestrict the rows returned by using the WHERE clause.The WHERE clause follows the FROM clause.SELECT [DISTINCT] {*| column [alias], ...}FROM table[WHEREcondition(s)];

Using the WHERE ClauseSQL> SELECT ename, job, deptno2 FROM emp3 WHERE job='CLERK';ENAME JOB DEPTNO---------- --------- ---------JAMES CLERK 30SMITH CLERK 20ADAMS CLERK 20MILLER CLERK 10

Character Strings and DatesCharacter strings and date values are enclosed in single quotation marks.Character values are case sensitive and date values are format sensitive.The default date format is DD-MON-YY.SQL> SELECTename, job, deptno2 FROM emp3 WHEREename = 'JAMES';

Comparison OperatorsOperator=> >= < <= <>MeaningEqual toGreater than Greater than or equal to Less than Less than or equal toNot equal to

Using the Comparison OperatorsSQL> SELECT ename, sal, comm2 FROM emp3 WHERE sal<=comm;ENAME SAL COMM---------- --------- ---------MARTIN 12501400

Other Comparison OperatorsOperatorBETWEEN...AND...IN(list)LIKEIS NULLMeaningBetween two values (inclusive) Match any of a list of values Match a character pattern Is a null value

Using the BETWEEN OperatorLowerlimitHigherlimitUse the BETWEEN operator to display rows based on a range of values.SQL> SELECTename, sal2 FROM emp3 WHEREsal BETWEEN 1000 AND 1500;ENAME SAL---------- ---------MARTIN 1250TURNER 1500WARD 1250ADAMS 1100MILLER 1300

Using the IN OperatorUse the IN operator to test for values in a list.SQL> SELECTempno, ename, sal, mgr2 FROM emp3 WHEREmgr IN (7902, 7566, 7788); EMPNO ENAME SAL MGR--------- ---------- --------- ---------7902 FORD 300075667369 SMITH 80079027788 SCOTT 300075667876 ADAMS 11007788

Using the LIKE OperatorUse the LIKE operator to perform wildcard searches of valid search string values.

Search conditions can contain either literal characters or numbers.

% denotes zero or many characters.

_ denotes one character.SQL> SELECTename2 FROM emp3 WHEREename LIKE 'S%';

Using the LIKE OperatorYou can combine pattern-matching characters.You can use the ESCAPE identifier to search for "%" or "_".SQL> SELECTename2 FROMemp3 WHEREename LIKE '_A%';ENAME---------- MARTINJAMES WARD

Using the IS NULL OperatorTest for null values with the IS NULL operator.SQL> SELECT ename, mgr2 FROM emp3 WHERE mgr IS NULL;ENAME MGR---------- ---------KING

Logical OperatorsOperatorANDORNOTMeaningReturns TRUE if both component conditions are TRUEReturns TRUE if either component condition is TRUEReturns TRUE if the following condition is FALSE

Using the AND OperatorAND requires both conditions to be TRUE.SQL> SELECT empno, ename, job, sal2 FROM emp3 WHERE sal>=11004 AND job='CLERK'; EMPNO ENAME JOB SAL--------- ---------- --------- ---------7876 ADAMS CLERK 11007934 MILLER CLERK 1300

Using the OR OperatorOR requires either condition to be TRUE.SQL> SELECT empno, ename, job, sal2 FROM emp3 WHERE sal>=11004 OR job='CLERK'; EMPNO ENAME JOB SAL--------- ---------- --------- ---------7839 KING PRESIDENT 50007698 BLAKE MANAGER 28507782 CLARK MANAGER 24507566 JONES MANAGER 29757654 MARTIN SALESMAN 1250 ... 7900 JAMES CLERK 950 ...14 rows selected.

Using the NOT OperatorSQL> SELECT ename, job2 FROM emp3 WHERE job NOT IN ('CLERK','MANAGER','ANALYST');ENAME JOB---------- ---------KING PRESIDENTMARTIN SALESMANALLEN SALESMANTURNER SALESMANWARD SALESMAN

Rules of PrecedenceOrder EvaluatedOperator1All comparison operators2NOT3AND4OROverride rules of precedence by using parentheses.

Rules of PrecedenceSQL> SELECT ename, job, sal2 FROM emp3 WHERE job='SALESMAN'4 OR job='PRESIDENT'5 AND sal>1500;ENAME JOB SAL---------- --------- ---------KING PRESIDENT 5000MARTIN SALESMAN 1250ALLEN SALESMAN 1600TURNER SALESMAN 1500WARD SALESMAN 1250

Rules of PrecedenceUse parentheses to force priority.SQL> SELECT ename, job, sal2 FROM emp3 WHERE (job='SALESMAN'4 OR job='PRESIDENT')5 AND sal>1500;ENAME JOB SAL---------- --------- ---------KING PRESIDENT 5000ALLEN SALESMAN 1600

ORDER BY ClauseSort rows with the ORDER BY clauseASC: ascending order, defaultDESC: descending orderThe ORDER BY clause comes last in the SELECT statement.SQL> SELECT ename, job, deptno, hiredate2 FROM emp3 ORDER BY hiredate;ENAME JOB DEPTNO HIREDATE---------- --------- --------- ---------SMITH CLERK 2017-DEC-80ALLEN SALESMAN 3020-FEB-81...14 rows selected.

Sorting in Descending OrderSQL> SELECT ename, job, deptno, hiredate2 FROM emp3 ORDER BY hiredate DESC;ENAME JOB DEPTNO HIREDATE---------- --------- --------- ---------ADAMS CLERK 2012-JAN-83SCOTT ANALYST 2009-DEC-82MILLER CLERK 1023-JAN-82JAMES CLERK 3003-DEC-81FORD ANALYST 2003-DEC-81KING PRESIDENT 1017-NOV-81MARTIN SALESMAN 3028-SEP-81...14 rows selected.

Sorting by Column AliasSQL> SELECT empno, ename, sal*12 annsal2 FROM emp3 ORDER BY annsal; EMPNO ENAME ANNSAL--------- ---------- ---------7369 SMITH 96007900 JAMES 114007876 ADAMS 132007654 MARTIN 150007521 WARD 150007934 MILLER 156007844 TURNER 18000...14 rows selected.

Sorting by Multiple ColumnsThe order of ORDER BY list is the order of sort.SQL> SELECT ename, deptno, sal2 FROM emp3 ORDER BY deptno, sal DESC;ENAME DEPTNO SAL---------- --------- ---------KING 105000CLARK 102450MILLER 101300FORD 203000...14 rows selected.You can sort by a column that is not in the SELECT list.SummarySELECT [DISTINCT] {*| column [alias], ...}FROM table[WHEREcondition(s)][ORDER BY{column, expr, alias} [ASC|DESC]];

Les02 Restricting And Sorting Data

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Les02 Restricting And Sorting Data