在DB2中拆分VARCHAR以检索其中的值

Question

我有一个VARCHAR包含5个以' ' 分隔的信息(2 CHAR(3)和3 TIMESTAMP)的列$.

CREATE TABLE MYTABLE (
  COL VARCHAR(256) NOT NULL
);

INSERT INTO MYTABLE 
VALUES
    ( 'AAA$000$2009-10-10 10:50:00$null$null$null' ),
    ( 'AAB$020$2007-04-10 10:50:00$null$null$null' ),
    ( 'AAC$780$null$2007-04-10 10:50:00$2009-04-10 10:50:00$null' )
;

我想提取第4场......

'AAA$000$2009-10-10 10:50:00$null$null$null'
                             ^^^^ this field

...有类似的东西

SELECT SPLIT(COL, '$', 4) FROM MYTABLE

1
-----
'null'
'null'
'2009-04-10 10:50:00'

我按顺序搜索:

1. DB2内置字符串函数
2. 一个可嵌入的声明,如SUBSTR(COL, POSSTR(COL)+1)...
3. 用户定义的函数,其行为类似于 SPLIT

精度:是的,我不知道这是不是有这样的列个好主意......

Answer 1

CREATE FUNCTION split(pos INT, delimeter CHAR, string VARCHAR(255))
LANGUAGE SQL
RETURNS VARCHAR(255)
DETERMINISTIC NO EXTERNAL ACTION
BEGIN ATOMIC
    DECLARE x INT;
    DECLARE s INT;
    DECLARE e INT;

    SET x = 0;
    SET s = 0;
    SET e = 0;

    WHILE (x < pos) DO
        SET s = locate(delimeter, string, s + 1);
        IF s = 0 THEN
            RETURN NULL;
        END IF;
        SET x = x + 1;
    END WHILE;

    SET e = locate(delimeter, string, s + 1);
    IF s >= e THEN
        SET e = LENGTH(string) + 1;
    END IF;
    RETURN SUBSTR(string, s + 1, e - s -1);
END!

用法:

SELECT split(3,'$',col) from mytable; -- or
SELECT split(0,'-', 'first-second-third') from sysibm.sysdummy1;
SELECT split(0,'-', 'returns this') from sysibm.sysdummy1;
SELECT split(1,'-', 'returns null') from sysibm.sysdummy1;