Restricting and Sorting Data

Copyright Oracle Corporation, 1998. All rights reserved.

22

Restricting and Sorting DataRestricting and Sorting Data

2-2

Limiting Rows Using a SelectionLimiting Rows Using a Selection

"…retrieve all"…retrieve allemployeesemployees

in department 10"in department 10"

EMPEMP

EMPNO ENAME JOB ... DEPTNO

7839 KING PRESIDENT 10 7698 BLAKE MANAGER 30 7782 CLARK MANAGER 10 7566 JONES MANAGER 20 ...

EMPEMP

EMPNO ENAME JOB ... DEPTNO

7839 KING PRESIDENT 10 7782 CLARK MANAGER 10 7934 MILLER CLERK 10

2-3

Limiting Rows SelectedLimiting Rows Selected

• Restrict the rows returned by using the WHERE clause.

• The WHERE clause follows the FROM clause.

• Restrict the rows returned by using the WHERE clause.

• The WHERE clause follows the FROM clause.

SELECT [DISTINCT] {*| column [alias], ...}FROM table[WHERE condition(s)];

2-4

Using the WHERE ClauseUsing the WHERE Clause

SQL> SELECT ename, job, deptno 2 FROM emp 3 WHERE job='CLERK';

ENAME JOB DEPTNO---------- --------- ---------JAMES CLERK 30SMITH CLERK 20ADAMS CLERK 20MILLER CLERK 10

2-5

Comparison OperatorsComparison Operators

Operator

=

>

>=

<

<=

<>

Meaning

Equal to

Greater than

Greater than or equal to

Less than

Less than or equal to

Not equal to

2-6

Using the Comparison Operators

Using the Comparison Operators

SQL> SELECT ename, sal, comm 2 FROM emp 3 WHERE sal<=comm;

ENAME SAL COMM---------- --------- ---------MARTIN 1250 1400

2-7

Other Comparison OperatorsOther Comparison Operators

Operator

BETWEEN

...AND...

IN(list)

LIKE

IS NULL

Meaning

Between two values (inclusive)

Match any of a list of values

Match a character pattern

Is a null value

2-8

Using the BETWEEN OperatorUsing the BETWEEN Operator

ENAME SAL---------- ---------MARTIN 1250TURNER 1500WARD 1250ADAMS 1100MILLER 1300

SQL> SELECT ename, sal 2 FROM emp 3 WHERE sal BETWEEN 1000 AND 1500;

Lowerlimit

Higherlimit

Use the BETWEEN operator to display Use the BETWEEN operator to display rows based on a range of values.rows based on a range of values.Use the BETWEEN operator to display Use the BETWEEN operator to display rows based on a range of values.rows based on a range of values.

2-9

Using the IN OperatorUsing the IN Operator

Use the IN operator to test for values in a Use the IN operator to test for values in a list.list.Use the IN operator to test for values in a Use the IN operator to test for values in a list.list.

SQL> SELECT empno, ename, sal, mgr 2 FROM emp 3 WHERE mgr IN (7902, 7566, 7788);

EMPNO ENAME SAL MGR--------- ---------- --------- --------- 7902 FORD 3000 7566 7369 SMITH 800 7902 7788 SCOTT 3000 7566 7876 ADAMS 1100 7788

2-10

Using the LIKE OperatorUsing the LIKE Operator

• Use 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.

• Use 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> SELECT ename 2 FROM emp 3 WHERE ename LIKE 'S%';

2-11

Using the LIKE OperatorUsing the LIKE Operator

• You can combine pattern-matching characters.

• You can use the ESCAPE identifier to search for "%" or "_".

• You can combine pattern-matching characters.

• You can use the ESCAPE identifier to search for "%" or "_".

SQL> SELECT ename 2 FROM emp 3 WHERE ename LIKE '_A%';

ENAME---------- MARTINJAMES WARD

2-12

Using the IS NULL OperatorUsing the IS NULL Operator

Test for null values with the IS NULL Test for null values with the IS NULL operator.operator.Test for null values with the IS NULL Test for null values with the IS NULL operator.operator.

SQL> SELECT ename, mgr 2 FROM emp 3 WHERE mgr IS NULL;

ENAME MGR---------- ---------KING

2-13

Logical OperatorsLogical Operators

Operator

AND

OR

NOT

Meaning

Returns TRUE if both component

conditions are TRUE

Returns TRUE if either component

condition is TRUE

Returns TRUE if the following condition is FALSE

2-14

Using the AND OperatorUsing the AND Operator

AND requires both conditions to be TRUE.AND requires both conditions to be TRUE.

SQL> SELECT empno, ename, job, sal 2 FROM emp 3 WHERE sal>=1100 4 AND job='CLERK';

EMPNO ENAME JOB SAL--------- ---------- --------- --------- 7876 ADAMS CLERK 1100 7934 MILLER CLERK 1300

2-15

Using the OR OperatorUsing the OR Operator

OR requires either condition to be TRUE.OR requires either condition to be TRUE.OR requires either condition to be TRUE.OR requires either condition to be TRUE.SQL> SELECT empno, ename, job, sal 2 FROM emp 3 WHERE sal>=1100 4 OR job='CLERK';

EMPNO ENAME JOB SAL--------- ---------- --------- --------- 7839 KING PRESIDENT 5000 7698 BLAKE MANAGER 2850 7782 CLARK MANAGER 2450 7566 JONES MANAGER 2975 7654 MARTIN SALESMAN 1250 ... 7900 JAMES CLERK 950 ...14 rows selected.

2-16

Using the NOT OperatorUsing the NOT Operator

SQL> SELECT ename, job 2 FROM emp 3 WHERE job NOT IN ('CLERK','MANAGER','ANALYST');

ENAME JOB---------- ---------KING PRESIDENTMARTIN SALESMANALLEN SALESMANTURNER SALESMANWARD SALESMAN

2-17

Rules of PrecedenceRules of Precedence

Override rules of precedence by using Override rules of precedence by using parentheses.parentheses.Override rules of precedence by using Override rules of precedence by using parentheses.parentheses.

Order Evaluated Operator

1 All comparison operators

2 NOT

3 AND

4 OR

2-18


ENAME JOB SAL---------- --------- ---------KING PRESIDENT 5000MARTIN SALESMAN 1250ALLEN SALESMAN 1600TURNER SALESMAN 1500WARD SALESMAN 1250

ENAME JOB SAL---------- --------- ---------KING PRESIDENT 5000MARTIN SALESMAN 1250ALLEN SALESMAN 1600TURNER SALESMAN 1500WARD SALESMAN 1250

SQL> SELECT ename, job, sal 2 FROM emp 3 WHERE job='SALESMAN' 4 OR job='PRESIDENT' 5 AND sal>1500;

2-19


ENAME JOB SAL---------- --------- ---------KING PRESIDENT 5000ALLEN SALESMAN 1600

ENAME JOB SAL---------- --------- ---------KING PRESIDENT 5000ALLEN SALESMAN 1600

Use parentheses to force priority.Use parentheses to force priority.Use parentheses to force priority.Use parentheses to force priority.

SQL> SELECT ename, job, sal 2 FROM emp 3 WHERE (job='SALESMAN' 4 OR job='PRESIDENT') 5 AND sal>1500;

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ORDER BY ClauseORDER BY Clause• Sort rows with the ORDER BY clause

– ASC: ascending order, default– DESC: descending order

• The ORDER BY clause comes last in the SELECT statement.

• Sort rows with the ORDER BY clause– ASC: ascending order, default– DESC: descending order

• The ORDER BY clause comes last in the SELECT statement.

SQL> SELECT ename, job, deptno, hiredate 2 FROM emp 3 ORDER BY hiredate;

ENAME JOB DEPTNO HIREDATE---------- --------- --------- ---------SMITH CLERK 20 17-DEC-80ALLEN SALESMAN 30 20-FEB-81...14 rows selected.

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Sorting in Descending OrderSorting in Descending Order

SQL> SELECT ename, job, deptno, hiredate 2 FROM emp 3 ORDER BY hiredate DESC;

ENAME JOB DEPTNO HIREDATE---------- --------- --------- ---------ADAMS CLERK 20 12-JAN-83SCOTT ANALYST 20 09-DEC-82MILLER CLERK 10 23-JAN-82JAMES CLERK 30 03-DEC-81FORD ANALYST 20 03-DEC-81KING PRESIDENT 10 17-NOV-81MARTIN SALESMAN 30 28-SEP-81...14 rows selected.

2-22

Sorting by Column AliasSorting by Column Alias

SQL> SELECT empno, ename, sal*12 annsal 2 FROM emp 3 ORDER BY annsal;

EMPNO ENAME ANNSAL--------- ---------- --------- 7369 SMITH 9600 7900 JAMES 11400 7876 ADAMS 13200 7654 MARTIN 15000 7521 WARD 15000 7934 MILLER 15600 7844 TURNER 18000...14 rows selected.

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Sorting by Multiple ColumnsSorting by Multiple Columns• The order of ORDER BY list is the order of

sort.• The order of ORDER BY list is the order of

sort.

• You can sort by a column that is not in the SELECT list.

• You can sort by a column that is not in the SELECT list.

SQL> SELECT ename, deptno, sal 2 FROM emp 3 ORDER BY deptno, sal DESC;

ENAME DEPTNO SAL---------- --------- ---------KING 10 5000CLARK 10 2450MILLER 10 1300FORD 20 3000...14 rows selected.

Copyright Oracle Corporation, 1998. All rights reserved.

22

Displaying Data from Multiple Tables

Displaying Data from Multiple Tables

2-25

EMPNO DEPTNO LOC----- ------- -------- 7839 10 NEW YORK 7698 30 CHICAGO 7782 10 NEW YORK 7566 20 DALLAS 7654 30 CHICAGO 7499 30 CHICAGO...14 rows selected.

EMPNO DEPTNO LOC----- ------- -------- 7839 10 NEW YORK 7698 30 CHICAGO 7782 10 NEW YORK 7566 20 DALLAS 7654 30 CHICAGO 7499 30 CHICAGO...14 rows selected.

Obtaining Data from Multiple TablesObtaining Data from Multiple TablesEMP EMP DEPT DEPT EMPNO ENAME ... DEPTNO------ ----- ... ------ 7839 KING ... 10 7698 BLAKE ... 30 ... 7934 MILLER ... 10

DEPTNO DNAME LOC ------ ---------- -------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON

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What Is a Join?What Is a Join?

Use a join to query data from more than Use a join to query data from more than one table.one table.

• Write the join condition in the WHERE clause.

• Prefix the column name with the table name when the same column name appears in more than one table.

Use a join to query data from more than Use a join to query data from more than one table.one table.

• Write the join condition in the WHERE clause.

• Prefix the column name with the table name when the same column name appears in more than one table.

SELECT table1.column, table2.columnFROM table1, table2WHERE table1.column1 = table2.column2;

SELECT table1.column, table2.columnFROM table1, table2WHERE table1.column1 = table2.column2;

2-27

Cartesian ProductCartesian 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 WHERE clause.

• 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 WHERE clause.

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Generating a Cartesian ProductGenerating a Cartesian Product

ENAME DNAME------ ----------KING ACCOUNTINGBLAKE ACCOUNTING ...KING RESEARCHBLAKE RESEARCH...56 rows selected.

ENAME DNAME------ ----------KING ACCOUNTINGBLAKE ACCOUNTING ...KING RESEARCHBLAKE RESEARCH...56 rows selected.

EMP (14 rows) EMP (14 rows) DEPT (4 rows) DEPT (4 rows)

EMPNO ENAME ... DEPTNO------ ----- ... ------ 7839 KING ... 10 7698 BLAKE ... 30 ... 7934 MILLER ... 10

EMPNO ENAME ... DEPTNO------ ----- ... ------ 7839 KING ... 10 7698 BLAKE ... 30 ... 7934 MILLER ... 10



““CartesianCartesianproduct: product:

14*4=56 rows”14*4=56 rows”

2-29

Types of JoinsTypes of Joins

EquijoinEquijoin Non-equijoinNon-equijoin Outer joinOuter join Self joinSelf join

2-30

What Is an Equijoin?What Is an Equijoin?EMP EMP DEPT DEPT EMPNO ENAME DEPTNO------ ------- ------- 7839 KING 10 7698 BLAKE 30 7782 CLARK 10 7566 JONES 20 7654 MARTIN 30 7499 ALLEN 30 7844 TURNER 30 7900 JAMES 30 7521 WARD 30 7902 FORD 20 7369 SMITH 20...14 rows selected.

DEPTNO DNAME LOC ------- ---------- -------- 10 ACCOUNTING NEW YORK 30 SALES CHICAGO 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 30 SALES CHICAGO 30 SALES CHICAGO 30 SALES CHICAGO 30 SALES CHICAGO 20 RESEARCH DALLAS 20 RESEARCH DALLAS...14 rows selected.

Foreign keyForeign key Primary keyPrimary key

2-31

Retrieving Records with Equijoins

Retrieving Records with Equijoins

SQL> SELECT emp.empno, emp.ename, emp.deptno, 2 dept.deptno, dept.loc 3 FROM emp, dept 4 WHERE emp.deptno=dept.deptno;

EMPNO ENAME DEPTNO DEPTNO LOC----- ------ ------ ------ --------- 7839 KING 10 10 NEW YORK 7698 BLAKE 30 30 CHICAGO 7782 CLARK 10 10 NEW YORK 7566 JONES 20 20 DALLAS...14 rows selected.

2-32

Qualifying Ambiguous Column Names

Qualifying Ambiguous Column Names

• Use table prefixes to qualify column names that are in multiple tables.

• Improve performance by using table prefixes.

• Distinguish columns that have identical names but reside in different tables by using column aliases.

• Use table prefixes to qualify column names that are in multiple tables.

• Improve performance by using table prefixes.

• Distinguish columns that have identical names but reside in different tables by using column aliases.

2-33

Additional Search ConditionsUsing the AND Operator

Additional Search ConditionsUsing the AND Operator

EMP EMP DEPT DEPT EMPNO ENAME DEPTNO------ ------- ------- 7839 KING 10 7698 BLAKE 30 7782 CLARK 10 7566 JONES 20 7654 MARTIN 30 7499 ALLEN 30 7844 TURNER 30 7900 JAMES 30 7521 WARD 30 7902 FORD 20 7369 SMITH 20...14 rows selected.

DEPTNO DNAME LOC ------ --------- -------- 10 ACCOUNTING NEW YORK 30 SALES CHICAGO 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 30 SALES CHICAGO 30 SALES CHICAGO 30 SALES CHICAGO 30 SALES CHICAGO 20 RESEARCH DALLAS 20 RESEARCH DALLAS...14 rows selected.

2-34

Using Table AliasesUsing Table Aliases

Simplify queries by using table aliases.Simplify queries by using table aliases.Simplify queries by using table aliases.Simplify queries by using table aliases.

SQL> SELECT emp.empno, emp.ename, emp.deptno,

2 dept.deptno, dept.loc

3 FROM emp, dept

4 WHERE emp.deptno=dept.deptno;

SQL> SELECT e.empno, e.ename, e.deptno,

2 d.deptno, d.loc

3 FROM emp e, dept d

4 WHERE e.deptno=d.deptno;

2-35

Joining More Than Two TablesJoining More Than Two Tables

NAME CUSTID----------- ------JOCKSPORTS 100TKB SPORT SHOP 101VOLLYRITE 102JUST TENNIS 103K+T SPORTS 105SHAPE UP 106WOMENS SPORTS 107... ...9 rows selected.

NAME CUSTID----------- ------JOCKSPORTS 100TKB SPORT SHOP 101VOLLYRITE 102JUST TENNIS 103K+T SPORTS 105SHAPE UP 106WOMENS SPORTS 107... ...9 rows selected.

CUSTOMER CUSTOMER

CUSTID ORDID------- ------- 101 610 102 611 104 612 106 601 102 602 106 604 106 605... 21 rows selected.

CUSTID ORDID------- ------- 101 610 102 611 104 612 106 601 102 602 106 604 106 605... 21 rows selected.

ORD ORD

ORDID ITEMID------ ------- 610 3 611 1 612 1 601 1 602 1...64 rows selected.

ORDID ITEMID------ ------- 610 3 611 1 612 1 601 1 602 1...64 rows selected.

ITEM ITEM

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Non-EquijoinsNon-EquijoinsEMPEMP SALGRADESALGRADE

““salary in the EMP salary in the EMP table is between table is between low salary and high low salary and high salary in the SALGRADEsalary in the SALGRADEtable”table”

EMPNO ENAME SAL------ ------- ------ 7839 KING 5000 7698 BLAKE 2850 7782 CLARK 2450 7566 JONES 2975 7654 MARTIN 1250 7499 ALLEN 1600 7844 TURNER 1500 7900 JAMES 950...14 rows selected.

GRADE LOSAL HISAL----- ----- ------1 700 12002 1201 14003 1401 20004 2001 30005 3001 9999

2-37

Retrieving Records with Non-Equijoins

Retrieving Records with Non-Equijoins

ENAME SAL GRADE---------- --------- ---------JAMES 950 1SMITH 800 1ADAMS 1100 1...14 rows selected.

SQL> SELECT e.ename, e.sal, s.grade

2 FROM emp e, salgrade s

3 WHERE e.sal

4 BETWEEN s.losal AND s.hisal;

2-38

Outer JoinsOuter Joins

EMP EMP DEPT DEPT

No employee in theNo employee in theOPERATIONS departmentOPERATIONS department

ENAME DEPTNO----- ------KING 10BLAKE 30CLARK 10JONES 20...

DEPTNO DNAME------ ----------10 ACCOUNTING30 SALES10 ACCOUNTING20 RESEARCH...40 OPERATIONS

2-39

Outer JoinsOuter Joins

• You use an outer join to also see rows that do not usually meet the join condition.

• Outer join operator is the plus sign (+).

• You use an outer join to also see rows that do not usually meet the join condition.

• Outer join operator is the plus sign (+).

SELECT table1.column, table2.column

FROM table1, table2

WHERE table1.column(+) = table2.column;


FROM table1, table2

WHERE table1.column(+) = table2.column;


FROM table1, table2

WHERE table1.column = table2.column(+);


FROM table1, table2

WHERE table1.column = table2.column(+);

2-40

Using Outer JoinsUsing Outer Joins

SQL> SELECT e.ename, d.deptno, d.dname

2 FROM emp e, dept d

3 WHERE e.deptno(+) = d.deptno

4 ORDER BY e.deptno;

ENAME DEPTNO DNAME---------- --------- -------------KING 10 ACCOUNTINGCLARK 10 ACCOUNTING... 40 OPERATIONS15 rows selected.

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Self JoinsSelf Joins

EMP (WORKER)EMP (WORKER) EMP (MANAGER)EMP (MANAGER)

““MGR in the WORKER table is equal to EMPNO in the MGR in the WORKER table is equal to EMPNO in the MANAGER table”MANAGER table”

EMPNO ENAME MGR----- ------ ---- 7839 KING 7698 BLAKE 7839 7782 CLARK 7839 7566 JONES 7839 7654 MARTIN 7698 7499 ALLEN 7698

EMPNO ENAME----- --------

7839 KING 7839 KING 7839 KING 7698 BLAKE 7698 BLAKE

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Joining a Table to ItselfJoining a Table to Itself

WORKER.ENAME||'WORKSFOR'||MANAG-------------------------------BLAKE works for KINGCLARK works for KINGJONES works for KINGMARTIN works for BLAKE...13 rows selected.

WORKER.ENAME||'WORKSFOR'||MANAG-------------------------------BLAKE works for KINGCLARK works for KINGJONES works for KINGMARTIN works for BLAKE...13 rows selected.

SQL> SELECT worker.ename||' works for '||manager.ename

2 FROM emp worker, emp manager

3 WHERE worker.mgr = manager.empno;

Restricting and Sorting Data

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