PostgreSQL , Oracle , 兼容函数 , Oracle compatible functions
PostgreSQL功能上基本可以和Oracle对齐，只是一些语法或者函数名不一样，所以为了做到兼容，有一些兼容包和兼容函数的出现。
PostgreSQL自带了一些Oracle兼容函数，如果你觉得不够意思，可以通过orafce插件继续扩展PostgreSQL与Oracle的兼容性(本文不涉及orafce包)。
http://pgxn.org/dist/orafce/
http://api.pgxn.org/src/orafce/orafce-3.3.0/README.asciidoc
在源码src/backend/utils/adt/oracle_compat.c中可以找到它们的定义
/*------------------------------------------------------------------------- * oracle_compat.c * Oracle compatible functions. * * Copyright (c) 1996-2016, PostgreSQL Global Development Group * * Author: Edmund Mergl <E.Mergl@bawue.de> * Multibyte enhancement: Tatsuo Ishii <ishii@postgresql.org> * * * IDENTIFICATION * src/backend/utils/adt/oracle_compat.c * *------------------------------------------------------------------------- */ /******************************************************************** * * lower * * Syntax: * * text lower(text string) * * Purpose: * * Returns string, with all letters forced to lowercase. * ********************************************************************/ /******************************************************************** * * upper * * Syntax: * * text upper(text string) * * Purpose: * * Returns string, with all letters forced to uppercase. * ********************************************************************/ /******************************************************************** * * initcap * * Syntax: * * text initcap(text string) * * Purpose: * * Returns string, with first letter of each word in uppercase, all * other letters in lowercase. A word is defined as a sequence of * alphanumeric characters, delimited by non-alphanumeric * characters. * ********************************************************************/ /******************************************************************** * * lpad * * Syntax: * * text lpad(text string1, int4 len, text string2) * * Purpose: * * Returns string1, left-padded to length len with the sequence of * characters in string2. If len is less than the length of string1, * instead truncate (on the right) to len. * ********************************************************************/ /******************************************************************** * * rpad * * Syntax: * * text rpad(text string1, int4 len, text string2) * * Purpose: * * Returns string1, right-padded to length len with the sequence of * characters in string2. If len is less than the length of string1, * instead truncate (on the right) to len. * ********************************************************************/ /******************************************************************** * * btrim * * Syntax: * * text btrim(text string, text set) * * Purpose: * * Returns string with characters removed from the front and back * up to the first character not in set. * ********************************************************************/ /******************************************************************** * * btrim1 --- btrim with set fixed as ' ' * ********************************************************************/ /******************************************************************** * * byteatrim * * Syntax: * * bytea byteatrim(byta string, bytea set) * * Purpose: * * Returns string with characters removed from the front and back * up to the first character not in set. * * Cloned from btrim and modified as required. ********************************************************************/ /******************************************************************** * * ltrim * * Syntax: * * text ltrim(text string, text set) * * Purpose: * * Returns string with initial characters removed up to the first * character not in set. * ********************************************************************/ /******************************************************************** * * ltrim1 --- ltrim with set fixed as ' ' * ********************************************************************/ /******************************************************************** * * rtrim * * Syntax: * * text rtrim(text string, text set) * * Purpose: * * Returns string with final characters removed after the last * character not in set. * ********************************************************************/ /******************************************************************** * * rtrim1 --- rtrim with set fixed as ' ' * ********************************************************************/ /******************************************************************** * * translate * * Syntax: * * text translate(text string, text from, text to) * * Purpose: * * Returns string after replacing all occurrences of characters in from * with the corresponding character in to. If from is longer than to, * occurrences of the extra characters in from are deleted. * Improved by Edwin Ramirez <ramirez@doc.mssm.edu>. * ********************************************************************/ /******************************************************************** * * ascii * * Syntax: * * int ascii(text string) * * Purpose: * * Returns the decimal representation of the first character from * string. * If the string is empty we return 0. * If the database encoding is UTF8, we return the Unicode codepoint. * If the database encoding is any other multi-byte encoding, we * return the value of the first byte if it is an ASCII character * (range 1 .. 127), or raise an error. * For all other encodings we return the value of the first byte, * (range 1..255). * ********************************************************************/ /******************************************************************** * * chr * * Syntax: * * text chr(int val) * * Purpose: * * Returns the character having the binary equivalent to val. * * For UTF8 we treat the argumwent as a Unicode code point. * For other multi-byte encodings we raise an error for arguments * outside the strict ASCII range (1..127). * * It's important that we don't ever return a value that is not valid * in the database encoding, so that this doesn't become a way for * invalid data to enter the database. * ********************************************************************/ /******************************************************************** * * repeat * * Syntax: * * text repeat(text string, int val) * * Purpose: * * Repeat string by val. * ********************************************************************/src/backend/utils/adt/oracle_compat.c
http://pgxn.org/dist/orafce/
http://api.pgxn.org/src/orafce/orafce-3.3.0/README.asciidoc
