PostgreSQL模仿MySQL的substring_index方法
https://www.iteye.com/blog/guanzhenxing-1617911
PostgreSQL中沒有substring_index方法,在做一個項目遷移的時候,需要類似MySQL的substring_index方法。從網上找了相關代碼。如下:
CREATE OR REPLACE FUNCTION substring_index(varchar, varchar, integer)
RETURNS varchar AS $$
DECLARE
tokens varchar[];
length integer ;
indexnum integer;
BEGIN
tokens := pg_catalog.string_to_array($1, $2);
length := pg_catalog.array_upper(tokens, 1);
indexnum := length - ($3 * -1) + 1;
IF $3 >= 0 THEN
RETURN pg_catalog.array_to_string(tokens[1:$3], $2);
ELSE
RETURN pg_catalog.array_to_string(tokens[indexnum:length], $2);
END IF;
END;
$$ IMMUTABLE STRICT LANGUAGE PLPGSQL;