Single Row Functions Part I Week 2

Objectives –Describe types of single row functions in SQL –Describe and use character, number and date SQL functions

Functions arg 1 arg 2 arg n Function Result 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, …

Conversion Character Number Date General Single-rowfunctions Types of Single Row Functions

Characterfunctions LOWERUPPERINITCAP CONCATSUBSTRLENGTHINSTRLPADTRIM Case conversion functions Character manipulation functions Single Row Character Functions

Case Conversion Functions FunctionResult 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> SELECTemployee_id, last_name, department_id FROMemployees WHERE last_name = ‘king'; no rows selected SQL> SELECTemployee_id, last_name, department_id FROMemployees WHERE 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> SELECTemployee_id, last_name, department_id FROMemployees WHERE LOWER(last_name) = ‘king'; SQL> SELECTemployee_id, last_name, department_id FROMemployees WHERE last_name = UPPER(‘King‘); no rows selected SQL> SELECTemployee_id, last_name, department_id FROMemployees WHERE last_name = UPPER(‘King‘); no rows selected Case Conversion Examples Display employee number, name and department number for employees named King

EMPLOYEE_ID LAST_NAME DEPARTMENT_ID 100 King 90 EMPLOYEE_ID LAST_NAME DEPARTMENT_ID 100 King 90 SQL> SELECTemployee_id, last_name, department_id FROMemployees WHERE INITCAP(last_name) = ‘King'; Case Conversion Examples (ctd) Display employee number, name and department number for employees named King EMPLOYEE_ID LAST_NAME DEPARTMENT_ID 100 King 90 EMPLOYEE_ID LAST_NAME DEPARTMENT_ID 100 King 90 SQL> SELECTempno, last_name, department_id FROMemployees WHERE 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) EMPLOYEE_ID LAST_NAME DEPARTMENT_ID 100 King 90 EMPLOYEE_ID LAST_NAME DEPARTMENT_ID 100 King 90 SQL> SELECTemployee_id, last_name, department_id FROMemployees WHERE 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 Character Manipulation Functions LENGTH(string)  Shows the length of a string as a numeric value Character Manipulation Functions INSTR(string, character)  Finds numeric position of first occurrence of a specified character Character Manipulation Functions 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 Character Manipulation Functions RPAD: pads a character value right-justified on a string Character Manipulation Functions 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 FunctionResult Examples using Character Manipulation Functions

Number Functions – Manipulate numeric values; frequently used functions include: ROUND, TRUNC, MOD ROUND(number, n): rounds number to n decimal places ROUND(43.826, 2)  ROUND(43.826, 0)  44 ROUND(43.826, -1)  40 TRUNC(number, n):truncates value to n decimal places TRUNC(43.826, 2)  TRUNC(43.826, 0)  43 TRUNC(43.826, -1)  40 MOD(number1, number2): returns remainder of number1 divided by number2 MOD(17, 3)  2

Date Functions – manipulate date data: most perform calculations on dates ADD_MONTHS(date, number): add or subtract a number of months from a date ADD_MONTHS(date, number): add or subtract a number of months from a date ADD_MONTHS(’22-JAN-01’,6)  22-JUL-01 MONTHS_BETWEEN(date1, date2) : number of months between dates MONTHS_BETWEEN(date1, date2) : number of months between dates MONTHS_BETWEEN(’22-JAN-01’, ’22-JUL-01)  -6 NEXT_DAY(date, day) returns the date for the next ‘day of the week’ from the date specified NEXT_DAY(date, day) returns the date for the next ‘day of the week’ from the date specified NEXT_DAY(’22-JAN-01’,’FRIDAY’)  26-JAN-01 LAST_DAY(date) returns the last day of the month for the date given LAST_DAY(date) returns the last day of the month for the date given LAST_DAY(’22-JAN-01’)  31-JAN-01

Date Functions (ctd) ROUND function can also be used on dates, rounding a date to the nearest month or year ROUND function can also be used on dates, rounding a date to the nearest month or year ROUND(’22-JAN-01’, ‘MONTH’)  01-FEB-01 ROUND(’22-JAN-01’,’YEAR’)  01-JAN-01 TRUNC function can also be used on dates, truncating a date to the nearest month or year TRUNC function can also be used on dates, truncating a date to the nearest month or year TRUNC(’22-JAN-01’, ‘MONTH’)  01-JAN-01 TRUNC(’22-JAN-01’,’YEAR’)  01-JAN-01

Querying Data Not Found in a Table Sometimes you may want to display data not stored in a table Sometimes you may want to display data not stored in a table However format of SELECT statement requires a FROM clause However format of SELECT statement requires a FROM clause In these situations refer to a small public table called DUAL which consists of one row of data for a single column and which therefore results in a single row of output In these situations refer to a small public table called DUAL which consists of one row of data for a single column and which therefore results in a single row of output Example: display today’s date: Example: display today’s date: SELECT SYSDATE FROM DUAL