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Oracle 常用功能函數匯總

2024-08-29 13:39:09
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  *******************************************************************************
  * SQL Group Functions (num can be a column or eXPRession)           *
  (null values are ignored, default between distinct and all is all)      *
  *******************************************************************************
  AVG([distinct or all] num)    average value
  COUNT(distinct or all] num)   number of values
  MAX([distinct or all] num)    maximum value
  MAX([distinct or all] num)    minimum value
  STDDEV([distinct or all] num)  standard deviation
  SUM([distinct or all] num)    sum of values
  VARIANCE([distinct or all] num) variance of values
   
  *******************************************************************************
  * Miscellaneaous Functions :                         *
  *******************************************************************************
  DECODE(expr, srch1, return1 [,srch2, return2...], default]
      if no search matches the expression then the default is returned,
      otherwise, the first search that matches will cause
      the corresponding return value to be returned
  DUMP(column_name [,fmt [,start_pos [, length]]])
      returns an internal Oracle format, used for getting info about a column
      format options : 8 = octal, 10 = decimel, 16 = hex, 17 = characters
      return type codes : 1 = varchar2, 2 = number, 8 = long, 12 = date,
       23 = raw, 24 = long raw, 69 = rowid, 96 = char, 106 = mlslabel
  GREATEST(expr [,expr2 [, expr3...]]
      returns the largest value of all expressions
  LEAST(expr [,expr2 [, expr3...]]
      returns the smallest value of all expressions
  NVL(expr1 ,expr2
      if expr1 is not null, it is returned, otherwise expr2 is returned
  SQLCODE
      returns sql error code of last error. Can not be used directly in query,
      value must be set to local variable first
  SQLERRM
      returns sql error message of last error. Can not be used directly in query,
      value must be set to local variable first
  UID
      returns the user id of the user you are logged on as
      useful in selecting information from low level sys tables
  USER
      returns the user name of the user you are logged on as
  USERENV('option')
      returns information about the user you are logged on as
      options : ENTRYID, sessionID, TERMINAL, LANGUAGE, LABEL, OSDBA
           (all options not available in all Oracle versions)
  VSIZE(expr)
      returns the number of bytes used by the expression
      useful in selecting information about table space requirements
   
  *******************************************************************************
  * SQL Date Functions (dt represents oracle date and time)           *
  * (functions return an oracle date unless otherwise specified)        *
  *******************************************************************************
  ADD_MONTHS(dt,
num)    adds num months to dt (num can be negative)
  LAST_DAY(dt)       last day of month in month containing dt
  MONTHS_BETWEEN(dt1, dt2) returns fractional value of months between dt1, dt2
  NEW_TIME(dt, tz1, tz2)  dt = date in time zone 1, returns date in time zone 2
  NEXT_DAY(dt, str)     date of first (str) after dt (str = 'Monday', etc..)
  SYSDATE          present system date
  ROUND(dt [,fmt]      rounds dt as specified by format fmt
  TRUNC(dt [,fmt]      truncates dt as specified by format fmt
   
  *******************************************************************************
  * Number Functions :                             *
  *******************************************************************************
  ABS(num)       absolute value of num
  CEIL(num)       smallest integer > or = num
  COS(num)       cosine(num), num in radians
  COSH(num)       hyperbolic cosine(num)
  EXP(num)       e raised to the num power
  FLOOR(num)      largest integer < or = num
  LN(num)        natural logarithm of num
  LOG(num2, num1)    logarithm base num2 of num1
  MOD(num2, num1)    remainder of num2 / num1
  POWER(num2, num1)   num2 raised to the num1 power
  ROUND(num1 [,num2]  num1 rounded to num2 decimel places (default 0)
  SIGN(num)       sign of num * 1, 0 if num = 0
  SIN(num)       sin(num), num in radians
  SINH(num)       hyperbolic sine(num)
  SQRT(num)       square root of num
  TAN(num)       tangent(num), num in radians
  TANH(num)       hyperbolic tangent(num)
  TRUNC(num1 [,num2]  truncate num1 to num2 decimel places (default 0)
   
  *******************************************************************************
  * String Functions, String Result :                      *
  *******************************************************************************
  (num)          ASCII character for num
  CHR(num)         ASCII character for num
  CONCAT(str1, str2)    str1 concatenated with str2 (same as str1str2)
  INITCAP(str)       capitalize first letter of each Word in str
  LOWER(str)        str with all letters in lowercase
  LPAD(str1, num [,str2]) left pad str1 to length num with str2 (default spaces)
  LTRIM(str [,set])    remove set from left side of str (default spaces)
  NLS_INITCAP(str [,nls_val]) same as initcap for different languages
  NLS_LOWER(str [,nls_val])  same as lower for different languages
  REPLACE(str1, str2 [,str3]) replaces str2 with str3 in str1
                 deletes str2 from str1 if str3 is omitted
  RPAD(str1, num [,str2])   right pad str1 to length num with str2 (default spaces)
  RTRIM(str [,set])      remove set from right side of str (default spaces)
  SOUNDEX(str)         phonetic representation of str
  SUBSTR(str,
num2 [,num1])  substring of str, starting with num2,
                 num1 characters (to end of str if num1 is omitted)
  SUBSTRB(str, num2 [,num1])  same as substr but num1, num2 expressed in bytes
  TRANSLATE(str, set1, set2)  replaces set1 in str with set2
                 if set2 is longer than set1, it will be truncated
  UPPER(str)          str with all letters in uppercase
   
  *******************************************************************************
  * String Functions, Numeric Result :                     *
  *******************************************************************************
   
  ASCII(str)             ASCII value of str
  INSTR(str1, str2 [,num1 [,num2]]) position of num2th occurrence of
                    str2 in str1, starting at num1
                    (num1, num2 default to 1)
  INSTRB(str1, str2 [,num1 [num2]]) same as instr, byte values for num1, num2
  LENGTH(str)            number of characters in str
  LENGTHB(str)            number of bytes in str
  NLSSORT(str [,nls_val])      nls_val byte value of str
   
  **********************************

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