Oracle TRANSLATE 函数

================原版官方解释==============================>

TRANSLATE ( 'expr' , 'from_string' , 'to_string' )

TRANSLATE returns expr with all occurrences of each character in from_string replaced by its corresponding character in to_string. Characters in expr that are not in from_string are not replaced. If expr is a character string, then you must enclose it in single quotation marks. The argument from_string can contain more characters than to_string. In this case, the extra characters at the end of from_string have no corresponding characters in to_string. If these extra characters appear in char, then they are removed from the return value.

You cannot use an empty string for to_string to remove all characters in from_string from the return value. Oracle Database interprets the empty string as null, and if this function has a null argument, then it returns null.

TRANSLATE provides functionality related to that provided by the REPLACE function. REPLACE lets you substitute a single string for another single string, as well as remove character strings. TRANSLATE lets you make several single-character, one-to-one substitutions in one operation.

This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion.

Examples

The following statement translates a book title into a string that could be used (for example) as a filename. The from_string contains four characters: a space, asterisk, slash, and apostrophe (with an extra apostrophe as the escape character). The to_string contains only three underscores. This leaves the fourth character in the from_string without a corresponding replacement, so apostrophes are dropped from the returned value.

SELECT TRANSLATE('SQL*Plus User''s Guide', ' */''', '___') FROM DUAL;

TRANSLATE('SQL*PLUSU
--------------------
SQL_Plus_Users_Guide


================粗略的汉字解释==============================>
TRANSLATE ( 'char' , 'from_string' , 'to_string' )

TRANSLATE返回将from_string中的每个字符替换为to_string中的相应字符以后的string。
TRANSLATE是REPLACE所提供的功能的一个超集。如果from_string比to_string长，那么在from_string中而不在to_string中的额外字符将从char中被删除，因为它们没有相应的替换字符。to_string不能为空。Oracle将空字符串解释为NULL，并且如果TRANSLATE中的任何参数为NULL，那么结果也是NULL。

举个例子--

select translate('123abc','2dc','4e') from dual;
因为from_string和to_string的位置是一一对应的，2对应4，d对应e，c没有对应的值，所以c应该会被删除。
所以例子的字符里的2会替换为4，
d因为字符串里没有，所以不作替换，
c由于没有对应的替换字符，所以字符串里的c会被删除
那么可以得出，结果是 143ab