2022年VF知识点总结 .pdf
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1、Visual Foxpro 程序设计基础一、重要知识点1.常量:a.数值型:占 8个字节b.货币型:占8 个字节,采用4 位小数,(四舍五入),如$123.456789将储存为$123.4568 c.字符型:(字符串)不包含任何字符的字符串是空串“”,空串与包含空格的字符串不同”(单双引号,方括号(定界符)都要是英文的)“?”换行,“?”不换行d.日期型:分隔符(/,.,空格);默认斜杠,8 个字节必须有脱字符 命令格式:1SET MARK TO 2SET DATE TO AMERICAN(mm/dd/yy默认)YMD(yy/mm/dd)3SET CENTURY ON|OFF|TO ROLLV
2、ER(ON 显示世纪,4 位数表示年份,1992)(OFF 不显示世纪,2 位,92,默认)(TO 解释一个用 2 位数字年份表示的日期所处的世纪,年份小于参照值,世纪值加1)4SET STRICTDATE TO 0|1|2(0 不进行严格的日期格式检查;1 进行,默认;2 进行)例:SET CENTURY ON SET MARK TO SET DATE TO YMD?2011-2-11 显示:2011/2/11 e.日期时间型:,默认 AM,8 个字节f.逻辑型:.T.t.Y.y.真,.F.f.N.n.假;两个句点不可少,是定界符。2.变量a,创建数组DIMESION y(2,2)b.内存变
3、量赋值1STORE TO 2=c.内存变量的显示1LIST MEMORY LIKE 通配符;一屏显示2DISPLAY MEMORY LIKE 通配符;多屏显示通配符有*和?,*表示任意多个字符;?表示任意一个字符例:LIST MEMORY LIKE A*表示只显示变量名以A 开头的所有内存变量d.内存变量的清除1CLEAR MEMORY 清除所有2RELEASE 3RELEASE ALL EXTENDED用于程序中 清除所有4RELEASE ALL LIKE 通配符 EXCEPT 通配符 LIKE 清除与通配符匹配的内存变量EXCEPT 清除与通配符不匹配的e表与表组之间的数据传递将表的当前记
4、录复制到数组SCATTER TO 将数组数据复制到表的当前记录GATHER FROM 3表达式A.数值表达式 +*/%(求余)B字符表达式 +:首尾相接:两字符串相连,前一个字符的尾部空格移到新字符串尾部 Len()用于计算字符串的长度 c.日期时间表达式日期+天数(后多少天);日期天数(前多少天);日期日期(得相差的天数);日期时间+秒数(多少秒后)日期时间秒数(多少秒前)日期时间日期时间(相差的秒数)d.关系表达式 =不等于(或#或!=)(字符串精确比较)$子串包含测试1.T.大于.F.$若字符 1 是字符 2 的一个子字符串,则结果为逻辑真,否则为逻辑假2设置字符排序次序命令:SET C
5、OLLATE TO“排序次序名”Machine:机内码,空格最前,大写ABCD,小写 abcd PinYin:拼音次序,空格最前,小写abcd,大写 ABCD Stroke:不论中西文,书写笔画3两字符串完全相同结果才为真 SET EXACT ON|OFF ON是尾部加上多个空格,使得两字符串的长度相等,OFF默认值,只要两者前面部分匹配就为逻辑真 e.逻辑表达式运算符:NOT AND OR 4.常用函数 A.数值函数1ABS()绝对值 SIGN()指定符号,运算结果分别为正、负和零时,输出 1、1、0 2SQRT 求平方根 PI()圆周率3求整数 INT()取整数部分 INT(5.8)=5
6、CEILING()取大于等于它的最小整数CEILING(5.8)=6 FLOOR()取小于等于它的最大整数FLOOR(5.8)=5 4四舍五入函数 ROUND(数值表达式 1,数值表达式 2)表达式 2 为四舍五入的位置ROUND(345.345,2)=345.35 ROUND(345.345,0)=345 ROUND(345.345,-1)=350 5求余 MOD(被除数 ,除数)余数符号同除数符号,被除数与除数同号时,函数值为两数相除的余数;异号时,函数值为相除的余数加上除数的值MOD(1O,3)(10除 以3)1 MOD(10,-3)=1+(-3)=-2 MOD(-10,-3)=-1 M
7、OD(-10,3)=-1+3=2 6最大最小 MAX()MIN()B.字符函数1字符串长度 LEN()大小写转换 LOWER()大到小 UPPER()小到大文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC
8、3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:C
9、C3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:
10、CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码
11、:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编
12、码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档
13、编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文
14、档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W32空格字符串生成 SPACE 3删除前后空格 TRIM()去后空格 LTRIM()去前空格 ALLTRIM()去前后空格4取子串 LEFT(表达式,长度)RIGHT(GOOD,2)6子串首字符位置 AT(字符表达式 1,字符表达式 2,第几次出现)ATC(同上)ATC不分大小写,AT分,默认第一次例:STORE“This is Visual Foxpro”TO x?AT(“fox”,x),ATC(“fox”,x),AT(“is”,x,3),AT(“xo”,x)0 16 10 0 7子串替换 STUFF(字符 1
15、,起始位置,长度,字符2)8字符替换 CHRTRAN(字符 1,字符 2,字符 3)9字符串匹配 LIKE(字符 1,字符 2)分大小写 C 日期和时间函数DATE()函数值为日期型 TIME()字符型 DATETIME()日期时间型 YEAR()MONTH()DAY()HOUR()MINUTE()SEC()D.数据类型转换函数1数值转换成字符 STR(数值表达式,长度(默认 10),小数位数(0))2字符串转换成数值 VAL(字符表达式)例:STORE-123.TO x STORE 45TO y STORE A45 TO z?VAL(x+y),Val(x+z),VAL(z+y)-123.45
16、 -123.00 0.00 3字符转换成日期 CTOD()或日期时间型 CTOT(W)4日期或日期时间转换成字符串DTOC()TTOC()5宏替换函数(字符型变量)&替换出字符变量得具体内容 E.测试函数1值域测试函数 BETWEEN 表达式 H 若值 L=T=H,则函数值为逻辑真,否则为逻辑假,L、H中有一个是 NULL值,则函数值也是 NULL值2空值 NULL 值测试函数 ISNULL表达式的运算结果是NULL值是,返回逻辑真,否则为逻辑假3“空”值测试函数 EMPTY EMPTY 结果是逻辑假4数据类型测试函数 VARTYPE 用 VARTYPE()测得的数据类型返回的字母数据类型返回
17、的字母数据类型C 字符型或备注型G 通用型N 数值型、整型、浮点或双精度型D 日期型Y 货币型T 日期时间型L 逻辑型X NULL值O 对象型U 未定义5表文件尾测试函数 EOF测试记录指针是否指向文件尾,是就返回逻辑真6表文件首 BOF 工作区号表别名文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文
18、档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3
19、文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W
20、3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9W3文档编码:CC3A6F4P10Y6 HN10K5Y1V3P2 ZZ10X1R1H9
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