Oracle 单字段拆分成多行详解数据库

方法一

SELECT DISTINCT 
    STUID, 
    REGEXP_SUBSTR (STUNAME, '[^,]+', 1, LEVEL) STUNAME, 
    STUSEX 
FROM 
    T_STU CONNECT BY LEVEL <= LENGTH (STUNAME) - LENGTH (REPLACE(STUNAME, ',', '')) + 1 
ORDER BY 
    STUID;

方法二

SELECT 
    STUID, 
    REGEXP_SUBSTR (STUNAME, '[^,]+', 1, lv) STUNAME, 
    STUSEX 
FROM 
    T_STU, 
    ( 
        SELECT 
            LEVEL lv 
        FROM 
            dual CONNECT BY LEVEL < 10 
    ) b 
WHERE 
    b.lv <= REGEXP_COUNT (T_STU.STUNAME, '/,') + 1 
ORDER BY 
    STUID;

方法三

SELECT stuid,substr(a.stuname, instr(a.stuname, ',', 1, levels.lvl) + 1, instr(a.stuname, ',', 1, levels.lvl + 1) -(instr(a.stuname, ',', 1, levels.lvl) + 1)) as stuname,stusex 
FROM  
(SELECT stuid,',' || stuname || ',' AS stuname,stusex,length(stuname) - nvl(length(REPLACE(stuname, ',')), 0) + 1 AS cnt --取待拆分字段每行按照分隔符','分割后的记录数，用于connect by 
FROM T_STU) a, 
(SELECT rownum AS lvl --产生一个待拆分字段分割后最大记录数的序列 
FROM (SELECT MAX(length(stuname || ',') - nvl(length(REPLACE(stuname, ',')), 0)) max_len FROM T_STU) 
CONNECT BY LEVEL <= max_len) levels 
WHERE levels.lvl <= a.cnt --笛卡尔连接 
ORDER BY stuid;

性能上方法三最优，其次方法二，方法一因为有distinct，性能可想而知