1. Introduction to Databases
Visual FoxPro & SQL

2. Database (數據庫) It is a collection of organised data.
It is organised so that data can be easily accessed and managed.
Example
Address book
Student record

3. Example - Student Record
Information to be stored:
Student ID
Name
Sex
DOB
Age
Remarks

4. Introduction To FoxPro
Starting up
click the FoxPro icon on “Office Toolbar”.
Setting up working folder
SET DEFAULT TO <working_folder>
Setting up the date format (i.e., mm/dd/yy)
SET STRICTDATE TO 0
Shutting down
type “QUIT” in the command window.

5. Data Types (數據類型)
In database, data are classified into different data types.
Character (字元)
Numeric (數值)
Date (日期)
Logical (邏輯)
Memo (附註)

6. Data Types (數據類型) (C)haracter (字元) Example “f00147” ‘f00147’
“Po King Wan”

7. Data Types (數據類型)
(N)umeric (數值)
Example
-25 12
123.45

8. Data Types (數據類型) (D)ate (日期) Example {12/25/99} {04/11/00}
Note that the default date format is American, i.e., mm/dd/yy

9. Data Types (數據類型)
(L)ogical (邏輯)
Example
.T. (True)
.F. (False)

10. Data Types (數據類型) (M)emo (附註)
This is a reference link to a file with an “FPT” extension.

11. Example - Student Record
Character
Information to be stored:
Student ID
Name
Sex
DOB
Age
Remarks
Character
Character
Date
Numeric
Memo

12. Notation

13. Print Command (?)
Question mark (?) is used to display result in the FoxPro window.
Syntax
? <exp1>[, <exp2>[, <exp3>]…]
Example ?
? “My age is”, 30

14. Unary Operators + -
Example
+4 - (-3)
+3 + (-2)
-2 + (-3)
-3 - (-3)

15. Arithmetic Operators addition (+) Example 123 + 456 subtraction (-)

16. Arithmetic Operators multiplication (*) Example 8 * 9 division (/)
16 / 4

17. Arithmetic Operators
exponentiation (^, **)
Example
3 ^ 2
2**3

18. Arithmetic Operators modulus (%), i.e., remainder of a / b where b  0
N.B. the sign of the result depends upon the divisor (b).
Example
5 % 3 = 2
-16 % 3 = 2
-5 % -3 = -2

19. Order of Precedence 1. Parentheses : “()” 2. Unary operators : “+, -”
3. Binary operators
(i) exponentiation : “^”
(ii) multiplication, division, modulo : “*, /, %”
(iii) addition, subtraction : “+, -”

20. Date Operations Adding/subtracting days
{mm/dd/yy}  n where n = 1, 2, 3, …
Example
?{12/10/99} + 12 = {12/22/99}
?{12/10/99} - 9 = {12/01/99}

21. Date Operations Finding number of days n = {mm/dd/yy} - {mm/dd/yy}
Example
?{11/22/99} - {10/29/99} = 24
?{12/31/98} - {01/01/98} = 364
Note that we CANNOT add (+) two dates together!

22. Character/String Operators
characters concatenation (+)
Example
?“Karen ” + “Kwong” = “Karen Kwong”
characters concatenation (-)
the trailing blanks are removed of the first string.
?“Irene ” - “Tse” = “IreneTse”

23. String Operators substring operator ($)
Usage:
A $ B
returns .T. if string A is contained in string B, .F. otherwise.
Note that characters are case sensitive.
Example
?“Chung” $ “Vincent Chung” = .T.
?“Chan” $ “Vincent Chung” = .F.

24. Relational Operators greater than (>) less than (<)
less than or equal to (<=)
greater than or equal to (>=)
equal to (=)
not equal to (<>, !=)

25. Logical Operators NOT AND OR negates the logical value.
returns true if all the logical values are true. OR
returns true if one of the logical values is true.

26. Logical Operator - NOT

27. Logical Operator - AND, OR

28. Variables (變數) variable refers to the contents in the computer memory.
each variable has a unique name.
Note
variable name must start with an alphabet
avoid using spaces and special characters except underscore (_).

29. Variables Assignment <var_name> = <value>
e.g., myName = “Vincent”
STORE <value> TO <var_name>
e.g., STORE 29 TO age

30. Variables Example x = 2 y = 5 ? x + y ? y ^ x z = {12/22/99} ? z + x
{12/24/99}
? y ^ x
z = {12/22/99}
? z + x

31. Variables Example x = 5 y = 10 ?x * y STORE 2 TO y ?x * y
data types mismatch,
outputs error message
STORE 2 TO y
?x * y
STORE “Tommy” TO y
?x + y

32. Function
f(x) x y
30
0.5
f(x) = sin x
Example

33. Functions
Character
Date and Time
Mathematical
Logical

34. Character Functions

35. Function - LEN()
returns the number of characters in a character expression
Syntax:
LEN(<expC>)
Example
?LEN(“Raymond”) 7

36. Function - UPPER() converts character string to upper case Syntax:
UPPER(<expC>)
Example
?UPPER(“Kennis Cheng”)
“KENNIS CHENG”

37. Function - LOWER() converts character string to lower case Syntax:
LOWER(<expC>)
Example
?LOWER(“Hang Seng”)
“hang seng”

38. Function - AT()
returns the numeric position of the occurence of <expC1> within <expC2>, starting from the leftmost character.
Syntax:
AT(<expC1>, <expC2> [, <expN>])
string to look for
string to be
searched
no. of occurrence,
default is 1

39. Function - AT() Example x = “what are you talking about?” ?AT(“a”, x)3 6 10
?AT(“a”, x, 2)
?AT(“you”, x)
?AT(“you”, x, 2)

40. Function - LEFT()
returns the specified number of leftmost characters from a character string
Syntax:
LEFT(<expC>, <expN>)
char.
expression
no. of char.
copied

41. Function - LEFT()
Example
?LEFT(“Ken Chan”, 3)
“Ken”

42. Function - RIGHT()
returns the specified number of rightmost characters from a character string
Syntax:
RIGHT(<expC>, <expN>)
char.
expression
no. of char.
copied

43. Function - RIGHT()
Example
?RIGHT(“Ken Chan”, 4)
“Chan”

44. Function - SUBSTR()
returns a specified number of characters from the given character string
Syntax:
SUBSTR(<expC>, <expN1> [, <expN2>])
char.
expression
starting
position
no. of char.
copied

45. Function - SUBSTR() Example ?SUBSTR(“Wong Ka Lun”, 6, 2)
“Tam”
?SUBSTR(“Wilson Tam”, 8) 5
x = “Chan Sze Lai”
?SUBSTR(x, AT(“ ”, x)+1)
“Sze Lai”

46. Function - STUFF()
returns a character string created by replacing a specified number of characters in a character string with another character string
Syntax:
STUFF(<expC1>, <expN1>, <expN2>, <expC2>)
no. of char.
to be replaced, if 0, the replacement char. is inserted into <expC1>
starting pos.
original char.
replacement
char.

47. Function - STUFF Example x = “She is smart” y = “hard-working”
?STUFF(x, 8, 5, y)
“She is hard-working”

48. “This is not really hard”
Function - STUFF()
Example
x = “This is hard”
y = “not really ”
?STUFF(x, AT(“ ”, x, 2)+1, 0, y) 8
“This is not really hard”

49. Function - STR()
returns the character string equivalent to a specified numeric expression
Syntax:
STR(<expN1>[, <expN2>[, <expN3>]])
numeric
expression
length of
character
no. of decimal
places

50. Function - STR() Example ?STR(29) ?STR(29.357, 6, 2)
“29”
“ 29.36”
?STR(29.357, 6, 2)
“29.4”
?STR(29.357, 4, 1)

51. Function - VAL()
returns a numeric expression from a specified character string composed of numbers
Syntax:
VAL(<expC>)

52. Function - VAL() Example ?VAL(“29”) ?VAL(“007”) ?VAL(“A160”)
?VAL(“007”)
280
?VAL(“A160”)
?VAL(“280T”)
2 X 103 = 2000
?VAL(“2E3”)

53. Function - ASC()
returns the ASCII code for the leftmost character in a character string.
Syntax:
ASC(<expC>)

54. Function - ASC()
Example
?ASC(“a”) 97 65
?ASC(“ACCURA”)

55. Function - CHR()
returns the character associated with the specified numeric ASCII code
Syntax:
CHR(<expN>)
Example
?CHR(100)
“d”

56. Function - ALLTRIM()
removes the leading and trailing space from the given string
Syntax:
ALLTRIM(<expC>)
Example
?ALLTRIM(“ HSSC ”)
“HSSC”

57. Function - LTRIM() removes the leading space from the given string
Syntax:
LTRIM(<expC>)
Example
?LTRIM(“ HSSC ”)
“HSSC ”

58. Function - RTRIM() / TRIM()
removes the trailing space from the given string
Syntax:
RTRIM(<expC>)
Example
?RTRIM(“ HSSC ”)
“ HSSC”

59. Function - SPACE()
returns a character string composed of a specified number of spaces
Syntax:
SPACE(<expN>)
Example
?“Karen” + SPACE(5) + “Wong”
“Karen Wong”

60. Reference Visual FoxPro & SQL - Ch2. p.38 - p.49
Practical Exercises (p.67)
Ex hand-in Monday

61. Date & Time Functions

62. Function - DATE() returns the current system date Syntax: DATE()
Example
?DATE()

63. Function - TIME() returns the current system time Syntax: TIME()
Example
?TIME()

64. Function - DAY() returns the day of <expD> Syntax:
DAY(<expD>)
Example
?DAY({09/01/98}) 1

65. Function - YEAR() returns the year of <expD> Syntax:
YEAR(<expD>)
Example
?YEAR(DATE())

66. Function - CMONTH() returns the month of <expD> Syntax:
CMONTH(<expD>)
Example
?CMONTH({02/28/00})
“February”

67. Function - MONTH() returns the numeric value of month of <expD>
Syntax:
MONTH(<expD>)
Example
?MONTH(DATE())

68. Function - CDOW() returns the day of week of <expD>. Syntax:
CDOW(<expD>)
Example
?CDOW({09/01/98}) = “Tuesday”

69. Function - DOW()
returns the numeric value of day of week of <expD>, i.e., Sunday starts from 1
Syntax:
DOW(<expD>)
Example
?DOW({09/01/98}) = 3

70. Function - CTOD() converts <expC> to date type Syntax:
CTOD(<expC>)
Example
?CTOD(“02/28/00”) = {02/28/00}

71. Function - DTOC() converts <expD> to character type Syntax:
DTOC(<expD>)
Example
?DTOC({02/12/99}) = “02/12/99”

72. Reference Visual FoxPro & SQL - Ch2. p.56 - p.59
Practical Exercise p.67
Ex. 13

73. Mathematical Functions

74. Function - ABS() returns an absolute value of <expN> Syntax:
ABS(<expN>)
Example
?ABS(2) = 2
?ABS(-12.5) = 12.5

75. Function - INT() returns an integer part of <expN> Syntax:
INT(<expN>)

76. Function - INT()
Example
?INT(3.25) 3 2 -2
?INT(2.58)
?INT(-2.5)

77. Function - ROUND()
returns a numeric expression rounded to a specified number of decimal places
Syntax:
ROUND(<expN1>, <expN2>)
number to
be rounded
no. of
decimal places

78. Function - ROUND() Example ?ROUND(10.475, 2) = 10.48

79. Function - SQRT() returns the square root of <expN> Syntax:
SQRT(<expN>)
Example
?SQRT(16) = 4

80. Function - MOD() returns the remainder of
<expN1> / <expN2> (<expN2>  0,
i.e., same as % operator)
Syntax:
MOD(<expN1>, <expN2>)

81. Function - MOD()
Example
?MOD(5, 3) = 2
?MOD(15, 8) = 7

82. Logical Functions
IIF

83. Function - IIF()
returns <exp1> if <expL> is true, <exp2> otherwise.
Syntax:
IIF(<expL>, <exp1>, <exp2>)

84. Function - IIF() It is like: IF <expL> = True THEN <exp1>
ELSE
<exp2>

85. Example
IF fifth_lesson = free THEN
lunch
ELSE
lesson

86. returns the first expression, i.e.,
Function - IIF()
Since 0<3 is true,
so the function
returns the first expression, i.e.,
“It is true”
Example
?IIF(0<3, “It is true”, “It is false”)
?IIF(MONTH(DATE())=2, “Feb”, “Others”)

87. More Example IF today = Sunday THEN family_day ELSE
IF today = Saturday THEN
go_out_with_friend
school_day

88. More Example ?IIF(CDOW(DATE())= “Sunday”, “family_day”,
IIF(CDOW(DATE()) = “Saturday”, “go_out”,
“school_day”))

89. Note 0 < x < 5 FoxPro cannot read this kind of condition.
We have to write
x > 0 AND x <5

90. Reference Visual FoxPro & SQL - Ch2. p.53 - p.56, p. 60
Practical Exercise p.68
Ex. 15

91. Creating A Database
Data Types
CREATE

92. Data Types Character (字元) Numeric (數值) Date (日期) Logical (邏輯)
Memo (附註)

93. Command - CREATE creates a new database file Syntax:
CREATE <filename>

94. Viewing/Modifying A Database Structure
LIST STRUCTURE
DISPLAY STRUCTURE
MODIFY STRUCTURE

95. Opening/Closing A Database File
USE
CLOSE ALL

96. Command - USE opens or closes a database Syntax:
USE [<filename>] [ALIAS <name>]

97. Command - CLOSE ALL
closes all opened files
Syntax:
CLOSE ALL

98. Viewing Database Records
LIST

99. Clearing FoxPro Screen

100. Reference
Visual FoxPro & SQL - Ch4. p.94 - p.99

101. Displaying Database Records
Produce a list to show the student’s name and class name.
Produce a list to show the student’s name who were born between 1981 and 1982.
Produce a list to show the name of female student in class 6B.

102. Record Pointer Database File Beginning of File Record 1 . Record n
End of File

103. Status Bar Total number of records Studrec 1 / 10 Current opened
database
Current record
i.e., a record that the record pointer pointed to

104. Moving The Record PointerGO
SKIP

105. Command - GO moves record pointer to a particular record Syntax:
GO [RECORD] <expN>
GO <TOP | BOTTOM>

106. Example Move the record pointer to the last record. GO BOTTOM
Move the record pointer to record 6.
Move the record pointer to the first record.
GO TOP

107. Command - SKIP moves record pointer forward or backward Syntax:
SKIP [<expN>]

108. Example Move the record pointer to the next record. SKIP
Current Record: 2
Move the record pointer to the next record.
SKIP
Current Record: 5
Move the record pointer to record 5.
SKIP 3
Current Record: 7
Move the record pointer 2 records forward.
SKIP 2
Current Record: 3
Move the record pointer 4 records backward.
SKIP -4

109. Displaying Database Records
show the current record of the current database.
LIST
show all the records of the current database.

110. Command - LIST shows all the records in the current database. Syntax:
LIST [[FIELDS] <field1>[, <field2>…]]
[<scope>]
[FOR <expL> | WHILE <expL>]
[TO PRINTER | TO FILE <filename>]

111. Command - DISPLAY shows the current record of the current database.
Syntax:
DISPLAY [[FIELDS] <field1>[, <field2>...]]
[<scope>]
[FOR <expL> | WHILE <expL>]
[TO PRINTER | TO FILE <filename>]

112. Example Produce a list to show the student’s name and class name.
LIST FIELDS name, class
LIST name, class

113. FOR
checks the logical value of <expL> starting from the first record to the last record.
returns the record only if the logical value of <expL> is TRUE.

114. Example - FOR
Produce a list to show the name of student who were born between 1981 and 1982.
LIST name FOR
YEAR(dob) >= 1981 AND
YEAR(dob) <= 1982

115. Example - FOR
Produce a list to show the name of female student in class 6B.
LIST name FOR
sex = “F” AND class = “6B”

116. WHILE
checks the logical value of <expL> starting from the current record.
returns the record only if the logical value of <expL> is TRUE.
stops checking when the logical value of <expL> is FALSE.

117. Example - WHILE GO TOP LIST WHILE sex = “M” GO 5 LIST WHILE sex = “F”
Current Record: 1
GO TOP
LIST WHILE sex = “M”
Current Record: 7
GO 5
LIST WHILE sex = “F”

118. Scope Keywords RECORD <expN> NEXT <expN> REST ALL
specifying particular record number
a range of records beginning with current record
a range of records beginning with current record to the last records
all records

119. Example - Scope Keyword
Produce a list to show all records by using command DISPLAY.
DISPLAY ALL
Show record number 4 by using command LIST.
LIST RECORD 4

120. Example - Scope Keyword
Starting from the current record, show the next 3 records.
LIST NEXT 3
Show the rest of the records.
LIST REST

121. Summary Moving Record Pointer Displaying Database Records
GO, SKIP
Displaying Database Records
DISPLAY, LIST
Setting Criteria
FOR, WHILE
Scope
RECORD, NEXT, REST, ALL

122. Reference Visual FoxPro & SQL, Ch. 4, p.99 - p.105
Practical Exercise p.122
Ex. 10, 12, 13, 14

123. Viewing/Modifying A Text File
TYPE
MODIFY FILE

124. Command - TYPE views the contents of a text file Syntax:
TYPE <file1>
[TO PRINTER | TO FILE <file2>]

125. Command - MODIFY FILE modifies the contents of a text file Syntax:
MODIFY FILE <filename>

126. Example USE studrec LIST name, dob FOR ave_mark < 60
TO FILE testing1
TYPE testing1.txt
MODIFY FILE testing1.txt
TYPE testing1.txt TO PRINTER
Note that the extention “TXT” must be specified.

127. Adding Database Records
APPEND
INSERT

128. Command - APPEND appends a blank record at the end of the database
Syntax:
APPEND [BLANK]

129. Command - INSERT
inserts a blank record before/after the current record
Syntax:
INSERT [BEFORE] [BLANK]

130. Deleting Database Records
DELETE
RECALL
PACK
ZAP

131. Command - DELETE marks a record as deleted Syntax:
DELETE [<scope>]
[FOR <expL> | WHILE <expL>]

132. Command - RECALL unmarks a deleted record Syntax:
RECALL [<scope>]
[FOR <expL> | WHILE <expL>]

133. Command -PACK
permanently removes the marked deleted record from the current database.
Syntax:
PACK

134. Command - ZAP
permanently removes all the records from the current database.
Syntax:
ZAP

135. Example DELETE FOR YEAR(dob) = 1982 LIST RECALL ALL
DELETE FOR DAY(dob) = 6
PACK
ZAP

136. Editing Database Records
BLANK
BROWSE
EDIT
REPLACE

137. Command - BLANK clears data in the current record Syntax:
BLANK [FIELDS <field1>[, <field2>...]] [<scope>]
[FOR <expL> | WHILE <expL>]

138. Example Clear the data in the name and dob fields in record 9.
BLANK FIELDS name, dob RECORD 9

139. Command - BROWSE opens a window in table (column) form Syntax:
BROWSE [FIELDS <field1>[, <field2>...]] [<scope>]
[FOR <expL> | WHILE <expL]

140. Example
Open the browse window to show the name, date of birth and average mark of male student.
BROWSE FIELDS name, dob, ave_mark
FOR sex = “M”

141. Command - EDIT opens a window in row form Syntax:
EDIT [FIELDS <field1>[, <field2>...]] [<scope>]
[FOR <expL> | WHILE <expL]

142. Example
Open an edit window to show the name and student identity for those who were born in 1983.
EDIT FIELDS name, stud_id
FOR YEAR(dob) = 1983

143. Command - REPLACE replaces data with the given values Syntax:
REPLACE <field1> WITH <exp1>
[, <field2> WITH <exp2>…]
[<scope>]
[FOR <expL> | WHILE <expL>]

144. Example Replace the average mark with 71.52 in record 7.
REPLACE ave_mark WITH RECORD 7

145. Example
For those who have not paid the school fee, have settled now. Update these records.
REPLACE paid WITH .T. FOR paid = .F.

146. Reference Visual FoxPro & SQL, Ch. 5 Practical Exercise p.153

147. Questions
In the name field, the surname “Yeung” is mistyped as “Yueng”. Correct it by using appropriate functions and command in one statement.
Add an extra field “AGE” to StudRec.
Then update the field “AGE” by using appropriate functions and command in one statement.

148. Questions REPLACE name WITH
LEFT(name, AT(“ ”, name)) + “Yeung” FOR “Yueng” $ name
REPLACE age WITH
INT((DATE() - dob)/365.25) ALL

149. Environment Variables
setups the FoxPro environment

150. Commands SET DEFAULT TO [<path>] SET PATH TO [<path>]
setups the working drive and folder.
SET PATH TO [<path>]
setups the path for searching files

151. Commands SET TALK ON | OFF ON shows the message on status bar. OFF
enables/disables results displayed on status bar. ON
shows the message on status bar.
OFF
hides the messages.

152. Commands SET DECIMALS TO [<expN>]
specifies the number of decimal places. The default is 2.
if the <expN> is omitted, the no. of decimal places is set back to default, i.e., 2.

153. Commands SET FIXED ON | OFF ON always shows the decimal places. OFF
specifies whether or not the number of decimal places used in the display of numeric data is fixed. ON
always shows the decimal places.
OFF
shows the decimal places only if the number consists of decimal places.

154. Example
SET FIXED ON
?5*5 = 25.00
SET FIXED OFF
?5*5 = 25

155. Commands SET EXACT ON | OFF
specifies the rules used when comparing two strings.

156. Example x = “Vincent” y = “Vincent Chung” SET EXACT OFF
? y = x (returns .T.)
SET EXACT ON
? y = x (returns .F.)

157. Commands SET FIELDS TO [<field1>[, <field2>…]]
specifies which field(s) can be accessed.
Note that this should be used with SET FIELDS ON | OFF.

158. Commands SET FIELDS ON | OFF ON shows the specified fields. OFF
specifies whether all fields or specific field(s) can be accessed. ON
shows the specified fields.
OFF
shows all the fields.

159. Example SET FIELDS TO name, dob, ave_mark SET FIELDS ON LIST
SET FIELDS OFF

160. Commands SET FILTER TO [<expL>]
specifies a condition that a record must meet to be accessible.
if <expL> is omitted, the filter is clear.

161. Example
SET FILTER TO sex = “F”
LIST
SET FILTER TO

162. Commands SET DELETED ON | OFF ON hides the marked deleted records. OFF
specifies whether or not to show the marked deleted record(s). ON
hides the marked deleted records.
OFF
shows the marked deleted records

163. Commands SET DATE TO [FORMAT]
specifies the format of the date. The default FORMAT is MDY.
FORMAT
MDY
DMY YM

164. Reference Visual FoxPro & SQL, Ch. 1, 2, 4 Practical Exercise p.124

165. Searching Database With Criteria
LOCATE
CONTINUE

166. Command - LOCATE finds a record with the specified criteria. Syntax:
LOCATE FOR <expL>
When the record is found, the record number is shown on the status bar.

167. Command - CONTINUE
continues to locate the rest of the records with the specified criteria
Syntax:
CONTINUE

168. Example
Find the database record whose average mark is greater than or equal to 70.
LOCATE FOR ave_mark >= 70
CONTINUE

169. Example Find the database record whose year of birth is 1981.
LOCATE FOR YEAR(dob) = 1981
CONTINUE

170. Other Functions
FOUND

171. Function - FOUND()
returns TRUE if a search is successful, FALSE otherwise.
Syntax:
FOUND()

172. Example
LOCATE FOR "Yeung" $ name
?FOUND()
CONTINUE

173. Reference Visual FoxPro & SQL, Ch. 6 - p.157 - 160
Practical Exercise p.195
Ex. 2, 3, 5

174. Database Sorting/Indexing (排序)
SET INDEX
SET ORDER
REINDEX

175. Command - SORT
sorts on particular field(s) and the sorted records are stored in a new database file
Syntax:
SORT ON <field1> [/A|/D] [/C]
[, <field2> [/A|/D] [/C] ...]
[<scope>]
[FOR <expL> | WHILE <expL>]
TO <file>

176. Command - SORT /A - ascending order /D - descending order
/C - ignores case

177. Note Wrong SORT can only sort field, expression is not allowed.
Example
SORT ON name, sex TO NameSex
SORT ON LEFT(name, 5) TO bbb
Wrong

178. Example
Sorts the records in descending order of NAME to a new database “dNameStud”.
USE StudRec
SORT ON name/D TO dNameStud
USE dNameStud
LIST

179. Example
Sorts the records in alphabetical order of SEX, for the same sex, sorts the records in descending order according to STUD_ID.
USE StudRec
SORT ON sex, stud_id/D TO SexIdStud
USE SexIdStud
LIST

180. Command - INDEX
sorts on particular field in ascending order, an index file with extension “IDX” will be created
Syntax:
INDEX ON <field1> [+ <field2>...]
TO <idx_file>

181. INDEX Example Index according to NAME Database File INDEX File
Rec
StudID
Name
Rec
Name
An INDEX file
is created 1
“F00123”
“Peter” 3
“David” 2
“F00007”
“John” 2
“John” 3
“F00001”
“David” 1
“Peter” 4
“F00014”
“Susan” 4
“Susan”

182. Note
index file stores the record addresses information, cannot be viewed
“+” can only be used if the data type of the fields to be joined are identical
to sort numeric expression in descending order, use “-1*<expN>”
INDEX can sort on expression

183. Example
By using INDEX command, sorts the records in ascending order of SURNAME, for the same surname, sorts the records according to STUD_ID.
USE studrec
INDEX ON
TRIM(SUBSTR(name, AT(“ ”, name) + 1)) +
stud_id TO xSurId
LIST

184. INDEX Example xSurId.IDX Rec
TRIM(SUBSTR(Name, AT(“ ”, Name) + 1)) + Stud_id 9
“Chans990210” 2
“Chengs990124” 8
“Cheungs990333” 4
“Chows990007”

185. Example
By using INDEX command, sorts the records in descending order of AVE_MARK.
INDEX ON -1 * ave_mark TO xDAveMk
LIST

186. INDEX Example xDAveMk.IDX Rec -1 * Ave_mark 2 -70.24 6 -65.89 3 -62.5010
-62.25

187. Comparison SORT INDEX Output: database file Output: index file
Order: asc. / desc.
Order: asc.
field only, no expression
e.g.,
SORT ON name TO dName
allows expression
e.g.,
INDEX ON LEFT(name, 3)
TO xName

188. Command - SET INDEX
opens one or more index files for use with the current database
Syntax:
SET INDEX TO [<idxfile1>[, <idxfile2>...]]

189. Command - SET ORDER
assigns a controlling index file for the current database
Syntax:
SET ORDER TO [<expN> | <idx_file>]

190. Command - REINDEX
updates the opened index files
Syntax:
REINDEX

191. Example USE StudRec INDEX ON name TO xName INDEX ON dob TO xDob
INDEX ON stud_id TO xStudid
CLOSE ALL

192. Example USE StudRec ** open the index file xName ** SET INDEX TO xName
LIST
** add a new record **
APPEND
LIST
** open the index file xDob **
SET INDEX TO xDob
LIST

193. Example ** update the index file xDob ** REINDEX LIST
** open the index file xStudid **
SET INDEX TO xStudid
LIST
** update the index file xStudid **
REINDEX
LIST
CLOSE ALL

194. Example USE StudRec ** open the index files xName, xDob and xStudid **
SET INDEX TO xName, xDob, xStudid
** add a new record **
APPEND

195. Example LIST ** using the index file xDob ** SET ORDER TO xDob LIST
** using the index file xStudid **
SET ORDER TO xStudid
LIST

196. Note - INDEX Order the records in ascending order of F1, then F2.
TESTING.DBF
Record
F1(N)
F2(N)
Record F1 F2 1 3 10 2 1 10 2 1 10 3 1 30 3 1 30 1 3 10

197. Note - INDEX INDEX ON F1 + F2 TO temp TESTING.DBF TEMP.IDX Record F13 10 2 11 2 1 10 1 13 3 1 30 3 31

198. Note - INDEX INDEX ON F1*1000 + F2 TO temp TESTING.DBF TEMP.IDX Record3 10 2
1010 2 1 10 3
1030 3 1 30 1
3010

199. Reference Visual FoxPro & SQL, Ch. 6 - p.161 - 175
Practical Exercise p.196
Ex. 8, 9

200. Searching Record in an Indexed Database
FIND
SEEK

201. INDEX Example Index according to NAME Database File INDEX File
Rec
StudID
Name
Rec
Name
An INDEX file
is created 1
“F00123”
“Peter” 3
“David” 2
“F00007”
“John” 2
“John” 3
“F00001”
“David” 1
“Peter” 4
“F00014”
“Susan” 4
“Susan”

202. Command - FIND
searches for the index key that matches the character expression
Syntax:
FIND <expC>
If the search is successful, the record pointer will point to that record, EOF otherwise.

203. Command - SEEK searches for the index key that matches the expression
Syntax:
SEEK <expression>
If the search is successful, the record pointer will point to that record, EOF otherwise.

204. Example USE studrec ** open the index files xName, xDob and xStudid **
SET INDEX TO xName, xDob, xStudid
FIND Victor
** using the index file xStudid **
SET ORDER TO xStudid
FIND s990210

205. Example ** using the index file xDob ** SET ORDER TO xDob
SEEK {01/06/83}
** using the index file xStudid **
SET ORDER TO xStudid
SEEK “s990333”

206. Comparison LOCATE FIND SEEK search database search index file
all data type.
char. only
all data type
except memo
allows condition
no condition
no condition
search next rec.
CONTINUE
search next rec.
SKIP
search next rec.
SKIP

207. Reference Visual FoxPro & SQL, Ch. 6 - p.179 - 185
Practical Exercise p.196
Ex. 12

208. Database Functions

209. Function - BOF()
determines whether the record pointer points at the beginning of the file
Syntax:
BOF()
BOF
Record 1 .
Record n
EOF

210. Function - EOF()
determines whether the record pointer points at the end of the file
Syntax:
EOF()
BOF
Record 1 .
Record n
EOF

211. Function - DELETED()
determines whether a record is marked deleted or not.
Syntax:
DELETED()
Example
LIST FOR DELETED() = .T.

212. Function - RECNO()
returns the current record number in the current database
Syntax:
RECNO()
Example
?RECNO()

213. Function - RECCOUNT()
returns the total number of records in the current database
Syntax:
RECCOUNT()
Example
?RECCOUNT()

214. Command - APPEND FROM
Adds records to the end of the current database from another database
Syntax:
APPEND FROM <database_file>
[FIELDS <field1> [,<field2>...]]
[FOR <expL>]

215. Command - APPEND FROM A.DBF B.DBF StudID Name “F00123” “Peter”
“John”
“F00001”
“David”
“F00014”
“Susan”
Rec 1 2 3 4
StudID
Name
“F00246”
“Peter”
“F00017”
“John”
“F00206”
“David”
Rec 1 2 3

216. Command - APPEND FROM ** open database A ** A.DBF USE A
** add records from B.DBF to
A.DBF **
APPEND FROM B
A.DBF
StudID
Name
“F00123”
“Peter”
“F00007”
“John”
“F00001”
“David”
“F00014”
“Susan”
Rec 1 2 3 4
“F00246”
“F00017”
“F00206” 5 6 7

217. Command - APPEND FROM A.DBF C.DBF StudID Name “F00123” “Peter”
“John”
“F00001”
“David”
“F00014”
“Susan”
Rec 1 2 3 4
“F00246”
“F00017”
“F00206” 5 6 7
Rec
StudID 1
“F00369” 2
“F00406”

218. Command - APPEND FROM ** add records from C.DBF to A.DBF A.DBF **
APPEND FROM C
A.DBF
StudID
Name
“F00123”
“Peter”
“F00007”
“John”
“F00001”
“David”
“F00014”
“Susan”
Rec 1 2 3 4
“F00246”
“F00017”
“F00206” 5 6 7
“F00369”
“F00406” 8 9

219. Example - Ch 5 - p.133
USE Metallic
APPEND FROM AddMetal
LIST

220. Command - COPY TO copies records to a new database file Syntax:
COPY TO <database_file>
[FIELDS <field1> [,<field2>...]]
[FOR <expL>]

221. Command - COPY TO A.DBF StudID Name “F00123” “Peter” “F00007” “John”
“David”
“F00014”
“Susan”
Rec 1 2 3 4
“F00246”
“F00017”
“F00206” 5 6 7

222. Command - COPY TO ** copies records to C.DBF ** COPY TO C
FOR VAL(SUBSTR(StudID, 2)) <= 50
C.DBF
StudID
Name
“F00007”
“John”
“F00001”
“David”
“F00014”
“Susan”
Rec 1 2 3
“F00017” 4

223. Data Set Calculations
COUNT
AVERAGE
SUM
TOTAL

224. Command - COUNT
counts the number of records in the current database. The result is shown on the status bar.
Syntax:
COUNT [<scope>]
[FOR <expL> | WHILE <expL>]
[TO <var>]

225. Command - COUNT A.DBF StaffID Name “C01” “Peter” “A10” “John” “M02”
“David”
“E09”
“Susan”
Rec 1 2 3 4
Salary
17000
18000
19000
20000
Sex
“M”
“F”

226. Example USE ch6ex12 ** find the total number of record ** COUNT
** find the total number of female records in the database **
COUNT FOR sex = “F”
** find the total number of record of “Sales” department and store the result to a variable x **
COUNT FOR department = “Sales” TO x

227. Command - AVERAGE
computes the arithmetic mean of the numeric expression / fields.
Syntax:
AVERAGE [<expression>]
[<scope>]
[FOR <expL> | WHILE <expL>]
[TO <var>]

228. Command - AVERAGE (17000 + 18000 + 19000 + 20000) / 4 A.DBF StaffID
Name
“C01”
“Peter”
“A10”
“John”
“M02”
“David”
“E09”
“Susan”
Rec 1 2 3 4
Salary
17000
18000
19000
20000
Sex
“M”
“F”
( ) / 4

229. Example USE ch6ex12 ** find the average of all numeric fields **
** find the average salary of female in the database **
AVERAGE salary FOR sex = “F”
** find the average salary of “Sales” department and store the result to a variable x **
AVERAGE salary
FOR department = “Sales” TO x

230. Command - SUM
finds the sum of the specified numeric field in the current database
Syntax:
SUM [<expression>]
[<scope>]
[FOR <expL> | WHILE <expL>]
[TO <var>]

231. Command - SUM 17000 + 18000 + 19000 + 20000 A.DBF Rec StaffID Name
Salary
Sex 1
“C01”
“Peter”
17000
“M” 2
“A10”
“John”
18000
“M” 3
“M02”
“David”
19000
“M” 4
“E09”
“Susan”
20000
“F”

232. Example USE ch6ex12 ** find the total of all numeric fields ** SUM
** find the total salary of “Account” department and store the result to a variable x **
SUM salary
FOR department = “Account” TO x

233. Command - TOTAL computes the total of numeric fields by group Syntax:
TOTAL ON <expression>
[<scope>]
[FOR <expL> | WHILE <expL>]
TO <file>

234. Note the database MUST BE indexed on the field to be grouped.
TOTAL computes the sum of NUMERIC fields only.

235. Command - TOTAL Group by sex A.DBF 17000 + 18000 + 19000 20000 Rec
StaffID
Name
Salary
Sex 1
“C01”
“Peter”
17000
“M”
19000 2
“A10”
“John”
18000
“M” 3
“M02”
“David”
19000
“M” 4
“E09”
“Susan”
20000
“F”
20000

236. Example (Ch 5 - p.149) USE fruit ** group the result by “fruit” **
INDEX ON fruit TO xFruit
TOTAL ON fruit TO temp1
USE temp1
LIST

237. Example USE fruit ** group the result by “class” **
INDEX ON class TO xClass
TOTAL ON class TO temp2
USE temp2
LIST

238. Example (Ch 5 - p.149) USE fruit ** group the result by “class” **
INDEX ON class TO xClass
TOTAL ON class TO temp2
USE temp2
LIST

239. Multiple Databases

240. Work Area FoxPro opens database in a work area
There are maximum 225 work areas in FoxPro, the default (預設值) is 1
Each work area is associated with an alias (別名) name, the default is the filename of the database, unless it is specified in the USE clause

241. Work Area 1
StudRec

242. Work Area 4
abc 3
studrec 2
sales 1
staff

243. Command - SELECT assigns the working area Syntax:
SELECT <expN> | <expC>

244. Example SELECT 1 USE Client SELECT 2 USE SalesOrder 1 Client
Rec Ptr: 1 2
SalesOrder
Rec Ptr: 1
SELECT 2
USE SalesOrder

245. Example SELECT 1 USE Client SELECT 2 USE SalesOrder GO 3 DISPLAY 1
Rec Ptr: 1 2
SELECT 2
USE SalesOrder
SalesOrder
Rec Ptr: 3
display record 3
GO 3
DISPLAY

246. Example SELECT 1 USE Client SELECT 2 USE SalesOrder GO 3 DISPLAY
Rec Ptr: 1
Display record 1
SELECT 1
USE Client
SELECT 2
USE SalesOrder 2
SalesOrder
GO 3
DISPLAY
Rec Ptr: 3
DISPLAY Client.Order_no

247. Command - SET RELATION
Parent
Child 2 1
Marks
Sreport

248. Note The two databases must have a COMMON FIELD
The common field in the CHILD DATABASE must be UNIQUE
The CHILD DATABASE must be INDEXED on that COMMON FIELD

249. Command - SET RELATION
establishes a relationship between two or more opened databases
Syntax:
SET RELATION TO [<exp> INTO <expC>, [<exp> INTO <expC>]...]

250. Example Sreport.dbf Marks.dbf “Stud_id” - common field.
“Stud_id” in Sreport is unique - child database.
“Stud_id” in Sreport must be indexed before setting the relationship

251. Example ** assign work area 1 ** SELECT 1
** open the child database “Sreport” **
USE Sreport
** index the common field “stud_id” **
INDEX ON Stud_id TO xStudid

252. Example ** assign work area 2 ** SELECT 2
** open the parent database “Marks” **
USE Marks
** establish the relationship to child “Sreport” through the common field “Stud_id” **
SET RELATION TO Stud_id INTO Sreport

253. Example
** produce a list to show the student name, subject code and mark **
LIST Sreport.Name, Sub_code, Mark

254. Example Subject.dbf Marks.dbf “Sub_code” - common field.
“Sub_code” in Subject is unique - child database.
“Sub_code” in Subject must be indexed before setting the relationship

255. Example ** assign work area ** SELECT 1
** open the child database “Subject” **
USE Subject
** index the common field “Sub_code” **
INDEX ON Sub_code TO xSubcode

256. Example ** assign work area ** SELECT 2
** open the parent database “Marks” **
USE Marks
** establish the relationship to child “Subject” through the common field “Sub_code” **
SET RELATION TO Sub_code INTO Subject

257. Example
** produce a list to show the student id, subject description and mark **
LIST Stud_id, Subject.Sub_desc, Mark

258. Example Sreport.dbf, Subject.dbf, Marks.dbf Stud_id Sub_code
common field of Sreport, Marks
unique in Sreport - child database
must be indexed
Sub_code
common field of Subject, Marks
unique in Subject - child database

259. Example SELECT 1 USE Sreport INDEX ON Stud_id TO xStudid SELECT 2
USE Subject
INDEX ON Sub_code TO xSubcode

260. Example SELECT 3 USE Marks SET RELATION TO Stud_id INTO Sreport,
Sub_code INTO Subject
LIST Sreport.Name, Subject.Sub_desc, Mark

261. Example
It was found that Victor Wong (f99001) his Maths mark was incorrectly entered as 8. The correct mark should be 68.
Assuming the relations between the databases have already been established.
Update the average mark of Victor Wong.

262. VIEW File
It is a file that stores all the information about the FoxPro environment.
Information includes:
the default path settings
databases, index file that are currently open in all work areas
relations between databases

263. Command - CREATE VIEW creates a view file from a FoxPro environment
Syntax:
CREATE VIEW <file>

264. Command - SET VIEW restores the FoxPro environment from a view file.
Syntax:
SET VIEW TO <file>

265. Example ** establish the relationship between “Subject” and “Marks” **
SELECT 1
USE Subject
INDEX ON Sub_code TO xSubcode
SELECT 2
USE Marks
SET RELATION TO Sub_code INTO Subject

266. Example
** create a view file to store the information in the FoxPro environment, i.e., the relationship between the databases **
CREATE VIEW Sreport
** close everything **
CLOSE ALL

267. Example
** open the view file to restore the information, i.e., the relationship between the databases **
SET VIEW TO Sreport
** produce a list to show the student id, subject description and mark **
LIST Stud_id, Subject.Sub_desc, Mark

268. One to One Linkage staff_id class c01 6A c02 6B c03 6C c04 6D a01 6E. . 6K 6L

269. One to Many Linkage staff_id class subject c01 6A CHN c02 6B CHN c03
ENG
c04 6D
CHN
a01 6E
CHN . . 6K
CHN 6L
ACC

270. Many to One Linkage staff_id class subject c01 6A CHN c02 6B CHN c03
ENG
c04 6C
CHN
a01 6D
CHN . . 6J
COM 6K
ACC

271. Command - UPDATE Master File Transaction File 2 1 Common field
Stock.dbf
Purchase.dbf

272. Command - UPDATE Master File Transaction File 2 1 itemNo Stock.dbf
Purchase.dbf
itemNo
Stock
itemNo
Qty
Date
010 5
011 5
4/1/99
011 2
013 7
4/1/99
012 7
010 4
4/1/99
013 1
011 5
4/2/99 .
013 4
4/2/99

273. Command - UPDATE Master File 2 Stock.dbf itemNo Stock 010 9 011 12 0127
013 12 .

274. Command - UPDATE
updates fields in the current database with data from another database open in another work area
Syntax:
UPDATE ON <common_field> FROM <expC>
REPLACE <field1> WITH <exp1>
[, <field2> WITH <exp2>...]

275. Note No need to set the relationship
Handle TWO databases only at a time
The two databases must have a COMMON KEY FIELD
Both databases must be INDEXED on that COMMON FIELD
Condition is not allowed, i.e., FOR

276. Example - UPDATE SELECT 1 USE Strgpurchase
INDEX ON Item_no TO xItemno1
SELECT 2
USE Strgstock
INDEX ON Item_no TO xItemno2
UPDATE ON Item_no FROM Strgpurchase
REPLACE Newqty WITH
Newqty + Strgpurchase.Qty

277. Example - SET RELATION SELECT 1 USE Strgstock
INDEX ON Item_no TO xItemno
SELECT 2
USE Strgpurchase
SET RELATION TO Item_no INTO Strgstock
REPLACE Strgstock.Newqty WITH
Strgstock.Newqty + Qty ALL

278. Creating A Report/Label
CREATE REPORT
CREATE LABEL

279. Command - CREATE REPORT
creates a report file
Syntax:
CREATE REPORT <file>

280. Example USE Teaching CREATE REPORT TeachRep
A report designer is open, run a quick report by executing the menu commands:
Report >> Quick Report

281. Modifying A Report/Label
MODIFY REPORT
MODIFY LABEL

282. Command - MODIFY REPORT
modifies a report file
Syntax:
MODIFY REPORT <file>

283. Example
USE Teaching
MODIFY REPORT TeachRep

284. Running A Report/Label
REPORT FORM
LABEL FORM

285. Command - REPORT FORM produces a report Syntax:
REPORT FORM <file> [<scope>]
[FOR <expL> | WHILE <expL>]
[PREVIEW | TO PRINTER]

286. Example
USE Teaching
REPORT FORM TeachRep
FOR Dept = “ACC” PREVIEW

287. Command - LABEL FORM produces a label Syntax:
LABEL FORM <file> [<scope>]
[FOR <expL> | WHILE <expL>]
[PREVIEW | TO PRINTER]

288. Data Grouping organises data into group.
field(s) to be grouped must be indexed.

289. Example
Produces a report to show the staff information that is group by department.
Staff_id
Name
Dept
c01
V Chan
COM
c02
A Chow
COM
c03
M Tam
COM
a01
L Wong
ACC
a02
S Lau
ACC .

290. Example Department COM Staff_id Name c01 V Chan c02 A Chow c03 M Tam
ACC
Staff_id
Name
a01
L Wong
a02
S Lau

291. Example USE Teaching INDEX ON Dept TO xDept MODIFY REPORT TeachRep
When report designer is open, executing the menu commands:
Report >> Data Grouping

292. Example
enters the field to be grouped,
i.e., Teaching.Dept

293. Data Dictionary information about tables (i.e., fields, type)
relations between tables (i.e., parent, child and their common field)
optionally stores the description of fields in another table

294. Command - SET VIEW ON
opens the Data Session Window to show the information about the tables.
Syntax:
SET VIEW ON

295. Command - COPY STRUCTURE EXTENDED
creates a file that stores the description of the fields of a table.
Syntax:
COPY STRUCTURE EXTENDED TO <file>

296. Copying Files
COPY FILE
COPY STRUCTURE

297. Command - COPY FILE makes a file copy. Syntax:
COPY FILE <file1> TO <file2>
Remember extension must be supplied

298. Command - COPY STRUCTURE
copies an existing database structure to a new file (no records are copied)
Syntax:
COPY STRUCTURE TO <filename>
[FIELDS <list>]