PG_全角转半角函数

CREATE OR REPLACE FUNCTION convertstring(text)

RETURNS text AS

$$

DECLARE

len INTEGER;

retval text;

tmp text;

asciival INT4;

difference INT4 := ascii('Ａ')-ascii('A');

fullCase char[] := ARRAY[ '！', '＃', '＄', '％', '＆', '（', '）', '＊', '＋', '，', '－', '．', '／', '：', '；', '＜', '＝', '＞', '？', '＠', '［', '］', '＾', '＿', '｛', '｜', '｝' ];

BEGIN

--文字数の取得

SELECT textlen($1) INTO len;

SELECT '' INTO retval;

--繰り返す

FOR i IN 1..len LOOP

--

SELECT substring($1, i, 1) INTO tmp;

SELECT ascii(tmp) INTO asciival;

BEGIN

--全角から半角に変更

IF (asciival >= ascii('Ａ')) AND (asciival <= ascii('Ｚ')) THEN

SELECT asciival-difference INTO asciival;

ELSIF (asciival >= ascii('ａ')) AND (asciival <= ascii('ｚ')) THEN

SELECT asciival-difference INTO asciival;

ELSIF (asciival >= ascii('０')) AND (asciival <= ascii('９')) THEN

SELECT asciival-difference INTO asciival;

ELSE

FOR j IN 0..array_length(fullCase , 1 ) LOOP

IF (asciival = ascii(fullCase[j])) THEN

SELECT asciival-difference INTO asciival;

END IF;

END LOOP;

END IF;

END;

SELECT chr(asciival) INTO tmp;

SELECT textcat(retval, tmp) INTO retval;

END LOOP;

RETURN retval;

END;

$$

LANGUAGE 'plpgsql';