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Chapter-5.ppt

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Chapter-5.ppt

  1. 1. Chapter 5 Single-Row Function(1)
  2. 2. Objectives  Understand the usage of functions in SELECT statements  Using Number and Text functions
  3. 3. What is Function?  A function is a type of procedure or routine that performs a specific task.  A function can receive argument and always returns a value. Sorting function F T G A R A F G R T
  4. 4. Two Types of SQL Functions Functions Single-row functions Multiple-row functions
  5. 5. Single-Row Functions  Manipulate data items  Accept arguments and return one value  Act on each row returned  Return one result per row  Can modify the data type  Can be nested
  6. 6. Single-Row Functions Single-row functions Number Text Date Conversion This chapter Chapter 6
  7. 7. Calling a Function in SQL function_name Is the name of the function column Is any named database column expression Is any character string or calculated expression arg1, arg2 Is any argument to be used by the function function_name (column|expression, [arg1, arg2,...])
  8. 8. Number Functions Function name Description Round (column/expression, precision) Round to a specified precision Mod Example: ( x mod y) Remainder after division Note: There are lots of other Number functions but the one highlights in the course is more useful
  9. 9. Using ROUND Function (a) Round Function SELECT Round(5.255,0) as [Round to 0], Round(5.255,1) as [Round to 1], Round(5.255,2) as [Round to 2] FROM test; Output: Round to 0 Round to 1 Round to 2 5 5.3 5.26
  10. 10. Using Mod Function It will return the remainder of a division. SELECT 10 mod 3 As [Mod] FROM test; Output: Mod 1
  11. 11. Text Functions Text functions UCase LCase StrConv Case conversion functions String manipulation functions Mid Trim Len Instr Left / Right
  12. 12. Case Conversion Functions Functions name Description UCase (column/expression) or StrConv(column/expression, 1) Puts all the letters in uppercase LCase (column/expression) or StrConv(column/expression, 2) Puts all the letters in lower case StrConv(column/expression, 3) Capitalizes the first letter of each word and puts all the other letters in lowercase.
  13. 13. Using UCase & LCase SELECT Ucase('smith') AS UpperCase, Lcase('SMITH') As LowerCase FROM test; Output: UpperCase LowerCase SMITH smith
  14. 14. Using StrConv SELECT StrConv('my name',1) as [UpperCase], StrConv('my name',2) as [LowerCase], StrConv('my name',3) as [Initial] FROM test; Output: UpperCase LowerCase Initial MY NAME my name My Name
  15. 15. Example of Case conversion SELECT Ucase (CourseDesp) as [Course Name] FROM Course; Output: Course Name DIPLOMA IN COMPUTER STUDIES DIPLOMA IN GAMING AND ANIMATION TECHNIQUES DIPLOMA IN COMPUTING DIPLOMA IN INFO-COMM TECHNOLOGY DIPLOMA IN INFORMATION TECHNOLOGY DIPLOMA IN NETWORK AND CYBERSECURITY
  16. 16. String Manipulation Functions  Perform operations of string such as creating a substring  Extract a portion of the string to create a new character string output  These functions are useful when you want to lookup certain data /values from a particular string.
  17. 17. String Manipulation Functions Functions Name Description Mid (stringexpression, start, length) Returns part of a string. Instr(start, stringexpression, search_string) Finds the occurrence of some search-string pattern Left(stringexpression, n) Or Right(stringexpression, n) Returns a portion of a string starting either left or right. Trim(stringexpression) Removes blanks spaces from both sides of a string Len(stringexpression) Returns the length of a string
  18. 18. MID Function Mid (stringexpression, start, length)  Stringexpression  The field or the value that will be use for the function to manipulate.  Start  Tells Access where in the stringexpression to start retrieving from  Length  The number of characters to extract. If the length is absent, then function will returns the rest of the string from where you start.
  19. 19. Example on MID function Output: Middle of String Rest of String Computer Computer Studies Gaming a Gaming and Animation Techniques Computin Computing Info-Com Info-Comm Technology Informat Information Technology Network Network and CyberSecurity SELECT Mid(CourseDesp,12,8) As [Middle of String], Mid(CourseDesp,12) As [Rest of String] FROM course;
  20. 20. INSTR Function Instr (start, stringexpression, search_string)  Start  Specify the position from which Access will start reading the stringexpression.  Stringexpression  The field or the value that will be use for searching.  Search_string  The value or the pattern that you looking for in the stringexpression
  21. 21. Example on INSTR Function Output: CourseDesp Position of C Diploma In Computer Studies 12 Diploma in Gaming and Animation Techniques 35 Diploma In Computing 12 Diploma In Info-Comm Technology 17 Diploma In Information Technology 26 Diploma in Network and CyberSecurity 24 SELECT CourseDesp, Instr(1,CourseDesp,'C') As [Position of C] FROM course;
  22. 22. LEFT / RIGHT Function Left (stringexpression, n) Or Right (stringexpression, n)  Stringexpression  The field or the value that will be use for manipulate.  n  The number of characters that will be returned from the stringexpression.
  23. 23. Example on LEFT/RIGHT function SELECT MentorName, Left(MentorName,3) As [Left], Right(MentorName,3) As [Right] FROM Mentor; Output MentorName Left Right Goile Goi ile Rimes Rim mes Christopher Chr her Schubert Sch ert Norman Nor man Carroll Car oll
  24. 24. TRIM Function Trim (stringexpression)  Stringexpression  The field or the value that spaces need to be removed
  25. 25. Example on TRIM function SELECT TRIM(‘ Hello ’) As [Greetings] …. Output: Greetings Hello
  26. 26. LEN Function Len (stringexpression)  Stringexpression  The field or the value that the length to be calculate.
  27. 27. Example on LEN Function SELECT MentorName, Len(MentorName) As [Length] FROM Mentor; Output: MentorName Length Goile 5 Rimes 5 Christopher 11 Schubert 8 Norman 6 Carroll 7
  28. 28. Using String Functions SELECT Mid(FirstName,1,Instr(1,FirstName,' ')) & ', ' & left(lastname,1) AS [Name] FROM Student; Output: Name Joseph , B Laura , K Choy , L Derrick , L Arthur , L Kathleen , M ………
  29. 29. Summary  Must know the features of Single-Row functions.  Usage of both Text and Number functions.

Notes de l'éditeur

  • Character Functions
    Single-row character functions accept character data as input and can return both character and number values. Character functions can be divided into:
    Case conversion functions: Convert the case of character strings
    Character manipulation functions: Perform operations of strings such as creating a substring
    This lesson covers the case conversion functions. Character manipulation functions are not covered in this course.
    Note: This list is a subset of the available character functions.
    For more information, see Oracle8 Server SQL Reference, “Character Functions.”

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