Question

 STUD_ID SUBJECT              GRADE

 1       math                 a
 1       english              b
 1       computer             c
 2       math                 c
 2       lang                 a
 3       phys                 a
 3       chem                 b

输出应该是这样的：

  stud_id   grades
    1       a,b,c
    2       c,a
    3       a,b

Answer 1

如果您使用的是Oracle 11g及更高版本，则可以使用 LISTAGG 字符串聚合功能。

例如，

*SELECT deptno, LISTAGG(ename, ',') WITHIN GROUP (ORDER BY ename) AS employees
FROM   emp
GROUP BY deptno;

    DEPTNO EMPLOYEES
---------- --------------------------------------------------
        10 CLARK,KING,MILLER
        20 ADAMS,FORD,JONES,SCOTT,SMITH
        30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD

3 rows selected.

对于其他特定于版本的解决方案，请参阅演示的示例here。

注意请记住，请勿使用wm_concat，它在之前的12c版本中没有记录，12c不支持。有关详细信息，请参阅我的回答here。

更新关于OP关于10g解决方案的请求。

Tim Hall的文章中提到了两种方式：

Oracle 10g

收集功能

例如，

CREATE OR REPLACE TYPE t_varchar2_tab AS TABLE OF VARCHAR2(4000);
/

CREATE OR REPLACE FUNCTION tab_to_string (p_varchar2_tab  IN  t_varchar2_tab,
                                          p_delimiter     IN  VARCHAR2 DEFAULT ',') RETURN VARCHAR2 IS
  l_string     VARCHAR2(32767);
BEGIN
  FOR i IN p_varchar2_tab.FIRST .. p_varchar2_tab.LAST LOOP
    IF i != p_varchar2_tab.FIRST THEN
      l_string := l_string || p_delimiter;
    END IF;
    l_string := l_string || p_varchar2_tab(i);
  END LOOP;
  RETURN l_string;
END tab_to_string;
/

ROW_NUMBER（）和 SYS_CONNECT_BY_PATH 在 Oracle 9i 及更高版本中运行

例如，

SELECT deptno, LTRIM(MAX(SYS_CONNECT_BY_PATH(ename,',')) KEEP (DENSE_RANK LAST ORDER BY curr),',') AS employees FROM (SELECT deptno, ename, ROW_NUMBER() OVER (PARTITION BY deptno ORDER BY ename) AS curr, ROW_NUMBER() OVER (PARTITION BY deptno ORDER BY ename) -1 AS prev FROM emp) GROUP BY deptno CONNECT BY prev = PRIOR curr AND deptno = PRIOR deptno START WITH curr = 1; DEPTNO EMPLOYEES ---------- -------------------------------------------------- 10 CLARK,KING,MILLER 20 ADAMS,FORD,JONES,SCOTT,SMITH 30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD 3 rows selected.

我想要输出而不使用Oracle 10g中的case或decode

1 个答案: