single row functions

Single Row Functions

Week 2

Objectives

– Describe types of single row functions in SQL

– Describe and use character, number, date, general and conversion SQL functions

Functions

arg 1arg 1

arg 2arg 2

arg arg nn

FunctionFunction

ResultResult

• All functions input 0, 1 or more arguments and output a single result.

• 2 basic types in SQL: Single row and Group

Single Row Functions

– Act on each individual row selected– Return one result per row retrieved from

table– Can be nested– Function can be used as part of expression

in: SELECT clause, WHERE clause, ORDER BY clause, …

– Argument for function may be any expression (literals, columns, arithmetic operators, …

ConversionConversion

CharacterCharacter

NumberNumber

DateDate

GeneralGeneralSingle-row Single-row functionsfunctions

Types of Single Row Functions

CharacterCharacterfunctionsfunctions

LOWERLOWER

UPPERUPPER

INITCAPINITCAP

CONCATCONCAT

SUBSTRSUBSTR

LENGTHLENGTH

INSTRINSTR

LPADLPAD

TRIMTRIM

Case conversion Case conversion functionsfunctions

Character manipulationCharacter manipulationfunctionsfunctions

Single Row Character Functions

Case Conversion Functions

Function Result

LOWER('Intro to SQL')

UPPER('Intro to SQL')

INITCAP('Intro to SQL')

intro to sql

INTRO TO SQL

Intro to Sql

– Convert case of character string data – Useful for matching when unsure of case used for column’s data or when case varies by row by row– UPPER: converts all characters to upper case– LOWER: converts all characters to lower case– INITCAP: converts first character of each word to upper case and remaining to lower case

SQL> SELECT employee_id, last_name, department_id FROM employeesWHERE last_name = ‘king';

no rows selected

SQL> SELECT employee_id, last_name, department_id FROM employeesWHERE last_name = ‘king';

no rows selected

EMPLOYEE_ID LAST_NAME DEPARTMENT_ID 100 King 90 EMPLOYEE_ID LAST_NAME DEPARTMENT_ID 100 King 90

SQL> SELECT employee_id, last_name, department_idFROM employeesWHERE LOWER(last_name) = ‘king';

SQL> SELECT employee_id, last_name, department_idFROM employeesWHERE last_name = UPPER(‘King‘);

no rows selected

SQL> SELECT employee_id, last_name, department_idFROM employeesWHERE last_name = UPPER(‘King‘);

no rows selected

Case Conversion ExamplesDisplay employee number, name and department number for employees named King


SQL> SELECT employee_id, last_name, department_idFROM employeesWHERE INITCAP(last_name) = ‘King';

Case Conversion Examples (ctd)Display employee number, name and department number for employees named King


SQL> SELECT empno, last_name, department_idFROM employeesWHERE UPPER(last_name) = ‘KING';

Case Conversion (ctd)Recommended: always use a case conversion function with column character data (except for unusual circumstances where case is significant in the data) and also always use a case conversion function with character substitution variables (except for unusual circumstances where case is significant in the data)


SQL> SELECT employee_id, last_name, department_id FROM employeesWHERE UPPER(last_name) = UPPER(‘&last_name’);

Character Manipulation Functions• CONCAT(string1, string2)Joins 2 character strings together

(You are limited to using only two parameters with CONCAT)

Character Manipulation Functions

• SUBSTR(string, start_position, length)Extracts a string of determined length from a specified starting position


• LENGTH(string)Shows the length of a string as a numeric value


• INSTR(string, character)Finds numeric position of first occurrence of a specified character


• LPAD(string, length, character)Places occurrences of a character (a blank is the default character) to the left of a string to end up with a specified length of character string


• RPAD: pads a character value right-justified on a string


• TRIM([{LEADING | TRAILING | BOTH}] character FROM string): removes occurrences of a leading and/or trailing (default is both leading and trailing) character (a blank is the default character) from a string

CONCAT('Good', 'Day')

SUBSTR('Good',3,2)

LENGTH('Good')

INSTR('Good', 'o')

LPAD(last_name,20,'*')

TRIM(‘$‘ FROM ‘$2,345‘)

GoodDay

od

4

2

****************King

2,345

Function Result

Examples using Character Manipulation Functions

Number Functions– Manipulate numeric values; frequently used functions Manipulate numeric values; frequently used functions include: ROUND, TRUNC, MODinclude: ROUND, TRUNC, MOD

ROUND(number, n): rounds number to n decimal placesROUND(number, n): rounds number to n decimal places

ROUND(43.826, 2)ROUND(43.826, 2) 43.8343.83

ROUND(43.826, 0)ROUND(43.826, 0) 4444

ROUND(43.826, -1)ROUND(43.826, -1) 4040

TRUNC(number, n):TRUNC(number, n): truncates value to n decimal placestruncates value to n decimal places

TRUNC(43.826, 2)TRUNC(43.826, 2) 43.8243.82

TRUNC(43.826, 0)TRUNC(43.826, 0) 4343

TRUNC(43.826, -1)TRUNC(43.826, -1) 4040

MOD(number1, number2): returns remainder of MOD(number1, number2): returns remainder of number1 divided by number2number1 divided by number2

MOD(17, 3)MOD(17, 3) 22

Date Functions– manipulate date data: most perform calculations on datesmanipulate date data: most perform calculations on dates

• ADD_MONTHS(date, number): add or subtract a ADD_MONTHS(date, number): add or subtract a number of months from a datenumber of months from a date

ADD_MONTHS(’22-JAN-01’,6)ADD_MONTHS(’22-JAN-01’,6) 22-JUL-0122-JUL-01

• MONTHS_BETWEEN(date1, date2) : number of months MONTHS_BETWEEN(date1, date2) : number of months between datesbetween dates

MONTHS_BETWEEN(’22-JAN-01’, ’22-JUL-01)MONTHS_BETWEEN(’22-JAN-01’, ’22-JUL-01) -6 -6

• NEXT_DAY(date, day) returns the date for the next NEXT_DAY(date, day) returns the date for the next ‘day of the week’ from the date specified‘day of the week’ from the date specified

NEXT_DAY(’22-JAN-01’,’FRIDAY’)NEXT_DAY(’22-JAN-01’,’FRIDAY’) 26-JAN-01 26-JAN-01

• LAST_DAY(date) returns the last day of the month for the LAST_DAY(date) returns the last day of the month for the date givendate given

LAST_DAY(’22-JAN-01’)LAST_DAY(’22-JAN-01’) 31-JAN-01 31-JAN-01

Date Functions (ctd)• ROUND function can also be used on dates, rounding ROUND function can also be used on dates, rounding a date to the nearest month or yeara date to the nearest month or year

ROUND(’22-JAN-01’, ‘MONTH’)ROUND(’22-JAN-01’, ‘MONTH’) 01-FEB-0101-FEB-01

ROUND(’22-JAN-01’,’YEAR’)ROUND(’22-JAN-01’,’YEAR’) 01-JAN-0101-JAN-01

• TRUNC function can also be used on dates, truncating a TRUNC function can also be used on dates, truncating a date to the nearest month or yeardate to the nearest month or year

TRUNC(’22-JAN-01’, ‘MONTH’)TRUNC(’22-JAN-01’, ‘MONTH’) 01-JAN-0101-JAN-01

TRUNC(’22-JAN-01’,’YEAR’)TRUNC(’22-JAN-01’,’YEAR’) 01-JAN-0101-JAN-01

General Functions• NVL(column, value): used to provide an actual value in NVL(column, value): used to provide an actual value in place of a NULL value for a columnplace of a NULL value for a column

SELECT employee_id, sal, comm, (NVL(sal,1000) + SELECT employee_id, sal, comm, (NVL(sal,1000) + NVL(comm,0)) AS COMPENSATION NVL(comm,0)) AS COMPENSATION

FROM employeesFROM employees

• DECODE(expression, condition1, result1 [, condition2, DECODE(expression, condition1, result1 [, condition2, result2], … [, default]): operates similarly to an IF- THEN-result2], … [, default]): operates similarly to an IF- THEN-ELSE statement in evaluating values in a columnELSE statement in evaluating values in a column

SELECT employee_id, job, DECODE(job,’President’,1, ‘Manager’, SELECT employee_id, job, DECODE(job,’President’,1, ‘Manager’, 2, ‘Developer’, 3, ‘Analyst’, 3, ‘Clerk’, 4) AS “JOB RANKING”2, ‘Developer’, 3, ‘Analyst’, 3, ‘Clerk’, 4) AS “JOB RANKING”


• SYSDATE: returns current system dateSYSDATE: returns current system date

SELECT employee_id, hiredateSELECT employee_id, hiredate


WHERE hiredate < ADD_MONTHS(SYSDATE, – 6)WHERE hiredate < ADD_MONTHS(SYSDATE, – 6)

Conversion Functions• many conversions in SQL occur implicitly, for example many conversions in SQL occur implicitly, for example string || numeric string || numeric string string• however in some cases a conversion function must be however in some cases a conversion function must be usedused

• TO_NUMBER(string, [format]): converts strings into TO_NUMBER(string, [format]): converts strings into numeric data - often used if numeric values have been numeric data - often used if numeric values have been stored using formatting of decimal points and numeric stored using formatting of decimal points and numeric separators; format specifies format of input dataseparators; format specifies format of input data

TO_NUMBER(‘1,234.56’, ‘9,999.99’)TO_NUMBER(‘1,234.56’, ‘9,999.99’)

• TO_CHAR(numeric data, [‘format’]): converts numeric TO_CHAR(numeric data, [‘format’]): converts numeric data to character data – normally used to format numeric data to character data – normally used to format numeric data (if format is not large enough to represent data then data (if format is not large enough to represent data then # symbols will be shown); format specifies output format# symbols will be shown); format specifies output format

TO_CHAR(sal, ‘$99,999.99’) TO_CHAR(sal, ‘$99,999.99’)

Conversion Functions(ctd)• TO_CHAR(date data, [‘format’]): converts date data to TO_CHAR(date data, [‘format’]): converts date data to character data – normally used to customize format of character data – normally used to customize format of date datadate data

TO_CHAR(’22-JAN-01’, ‘DAY MONTH DD, YYYY’) TO_CHAR(’22-JAN-01’, ‘DAY MONTH DD, YYYY’) THURSDAY JANUARY 22, 2001THURSDAY JANUARY 22, 2001

Date Format Symbols used in Date ConversionDate Format Symbols used in Date ConversionDay:Day: Day of the weekDay of the weekDY:DY: Abbreviated day of the weekAbbreviated day of the weekDD: DD: 2 digit day value2 digit day valueMM: MM: 2 digit month value2 digit month valueMON:MON: Abbreviated month nameAbbreviated month nameMONTH:MONTH: Month nameMonth nameYYYY:YYYY: 4 digit year value4 digit year valueYEAR:YEAR:Year value in wordsYear value in wordsQ:Q: Quarter of the year (1Quarter of the year (1stst – 4 – 4thth))

Conversion Functions (ctd)• TO_DATE(string, ‘format’): converts strings into data in TO_DATE(string, ‘format’): converts strings into data in Oracle’s internal date formatOracle’s internal date format

SELECT employee_id, hiredateSELECT employee_id, hiredate


WHERE hiredate = TO_DATE(‘September 28, WHERE hiredate = TO_DATE(‘September 28, 1981’, ‘Month DD, YYYY’)1981’, ‘Month DD, YYYY’)

Nesting of Functions• Single row function calls can be nested within each Single row function calls can be nested within each otherother

• Innermost function is evaluated firstInnermost function is evaluated first

• Example – show the review dates for all employees Example – show the review dates for all employees where review date is first Monday occurring 3 months after where review date is first Monday occurring 3 months after starting work:starting work:

SELECT employee_id, NEXT_DAY(ADD_MONTHS(hiredate, 3) , SELECT employee_id, NEXT_DAY(ADD_MONTHS(hiredate, 3) , ‘MONDAY’) AS “FIRST REVIEW DATE”, (sal + NVL(comm,0)) AS ‘MONDAY’) AS “FIRST REVIEW DATE”, (sal + NVL(comm,0)) AS COMPENSATIONCOMPENSATION


Querying Data Not Found in a Table

• Sometimes you may want to display data not stored in a Sometimes you may want to display data not stored in a tabletable

• However format of SELECT statement requires a FROM However format of SELECT statement requires a FROM clauseclause

• In these situations refer to a small public table called In these situations refer to a small public table called DUAL which consists of one row of data for a single column DUAL which consists of one row of data for a single column and which therefore results in a single row of outputand which therefore results in a single row of output

• Example: display today’s date:Example: display today’s date:

SELECT SYSDATESELECT SYSDATE

FROM DUALFROM DUAL

single row functions

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