drop function if exists str_for_substr;
CREATE
    DEFINER = `root`@`%` FUNCTION `str_for_substr`(`num` int, `str` varchar(5000))
    RETURNS varchar(100) no sql
BEGIN
    /*函數(shù)功能: 把帶逗號的字符串分割取出
        參數(shù): num 要取出的字符串的索引值, 以0開始
                    str 以逗號分割的字符串
        擴展: 將###替換成其他符合，即可完成不同分隔符拆分字符串，亦可以把分隔符作為參數(shù)
  */
    SET @str_for_substr =
            SUBSTRING(
                    SUBSTRING_INDEX(str, '###', num + 1),
                    CASE num
                        WHEN 0 THEN
                                CHAR_LENGTH(
                                        SUBSTRING_INDEX(str, '###', num)
                                    ) + 1
                        ELSE
                                CHAR_LENGTH(
                                        SUBSTRING_INDEX(str, '###', num)
                                    ) + 4
                        END,
                    CASE num
                        WHEN 0 THEN
                                CHAR_LENGTH(
                                        SUBSTRING_INDEX(str, '###', num + 1)
                                    ) - CHAR_LENGTH(
                                        SUBSTRING_INDEX(str, '###', num)
                                    )
                        ELSE
                                CHAR_LENGTH(
                                        SUBSTRING_INDEX(str, '###', num + 1)
                                    ) - CHAR_LENGTH(
                                        SUBSTRING_INDEX(str, '###', num)
                                    ) - 1
                        END
                );
    RETURN @str_for_substr;
END;

drop procedure if exists split_str;
CREATE
    DEFINER = `root`@`%` PROCEDURE `split_str`()

BEGIN

    DECLARE cnt int default 0;
    DECLARE num int default 0;
    DECLARE i int default 0;
    DECLARE j int default 0;
    declare str varchar(4000);

#   統(tǒng)計當前截取字段表的數(shù)據(jù)量
    select count(1) into cnt from test;
#   循環(huán)查詢每一條數(shù)據(jù)，此處可以換成游標處理
    while i<= cnt do
        select query_knowledge_list_string into str from test limit i,1;
#       查詢每條數(shù)據(jù)###出現(xiàn)的次數(shù)
        SET num = (LENGTH(str) - LENGTH(REPLACE(str, '###', ''))) / 3;
        while j <= num do
#               循環(huán)插入截取后的數(shù)據(jù)
                INSERT INTO test1 (knowledge_name, subject_name, grade_name)
                select str_for_substr(j,str), subjectName, grade_name
                from test limit i,1;
            set j = j + 1;
            end while;
#       循環(huán)值歸零
        set j = 0;
        set i = i + 1;
        end while;
END;

select 
year,
case when INSTR(subtype,'、')>0 then SUBSTR(subtype,INSTR(subtype,'、')+1)
else subtype END subtype
from 
xxx_table_name