Operator Precedence

SQL> SELECT ename, sal, 12*sal+100 2 FROM emp;

14 rows selected.

1-12

Usingi Parentheses

SQL> SELECT ename, sal, 12*(sal+100) 2 FROM emp;

14 rows selected.

1-13

Definingi i a Nullll Valuel

•• A nullll isis a valuel thatt t isis unavailable,il l , unassigned,i , unknown,, orr inapplicablei li le..

•• A nullll isis nott thet same as zeroro orr a blankl space..

14 rows selected.

1-14

Nullll Valuesl inin Arithmetici ic Expressionsi

Arithmetic expressions containing a null value evaluate to null.

1-15

Definingi i a Columnl Aliasli

•• Renames a columnl headingi

•• IsIs usefulf l withith calculationsl l ti

•• ImmediatelyI i t ly followsf llo columnl name;; optionalti l AS keywordrd betweent columnl name and aliasli

•• Requiresir doublele quotationt ti marksr ifif itit containst i spaces orr speciali l charactersr t rs orr isis case sensitiveiti

1-16

Usingi Columnl Aliasesli

SQL> SELECT ename AS name, sal salary 2 FROM emp;

SQL> SELECT ename "Name",

2 sal*12 "Annual Salary"

3 FROM emp;

Name Annual Salary

------------- -------------

...

1-17

Concatenationi Operator

•• Concatenatest t columnsl orr characterr t r stringstri toto othert r columnsl

•• IsIs representedr r t by ttwo verticalrti l barsrs (||)(||)

•• Createsr t a resultantr lt t columnl thatt t isis a characterr t r expressionr i

1-18

Usingi the Concatenationi

Operator

Employees

-------------------

KINGPRESIDENT

BLAKEMANAGER

CLARKMANAGER

JONESMANAGER

MARTINSALESMAN

ALLENSALESMAN

...

14 rows selected.

1-19

Literali l Character Stringsi

•• A literallit r l isis a character,r t r, expression,r i , orr numberr includedi l inin thet SELECT listli t..

•• Datete and characterr t r literallit r l valuesl mustt be enclosedl withinit in singlei le quotationt ti marksr ..

•• Each characterr t r stringtri isis outputt t once forf r each rowro returnedr t r ..

1-20

Usingi Literali l Character Stringsi

SQL> SELECT ename ||''||'is a'||''||job 2 AS "Employee Details"

3 FROM emp;

Employee Details

-------------------------

KING is a PRESIDENT BLAKE is a MANAGER

CLARK is a MANAGER

JONES is a MANAGER

MARTIN is a SALESMAN

...

14 rows selected.

1-21