oracle之listagg()函数

-- 查询部门为20的员工列表

 SELECT t.DEPTNO,t.ENAME FROM SCOTT.EMP t where t.DEPTNO = '20';

 SELECT T.DEPTNO,       LISTAGG (T.ENAME, ',') WITHIN GROUP (ORDER BY T.ENAME) AS NAMES FROM SCOTT.EMP T WHERE T.DEPTNO = '20' GROUP BY T.DEPTNO;

 SELECT     T.DEPTNO,     LISTAGG(T.ENAME,',') WITHIN GROUP (ORDER BY T.ENAME) OVER(PARTITION BY T.DEPTNO) as ENAME FROM   SCOTT.EMP T WHERE T.DEPTNO = '20';

4、XMLAGG

语句一：结果中的聚合字段是CLOB类型，是文本字符。处理400多万条数据，运行时间是20分钟。

 SELECT T.DEPTNO,LTRIM(XMLAGG(XMLELEMENT(T,',',T.ENAME)ORDER BY T.ENAME).EXTRACT('//text()').GETCLOBVAL(),',') AS NAMES    FROM SCOTT.EMP T   WHERE T.DEPTNO=20 GROUP BY T.DEPTNO;

如下：

语句二：结果汇总的聚合字段也是clob类型，不过是hex字节；处理400多万条数据，运行时间是56秒

 SELECT T.DEPTNO,        RTRIM(XMLAGG(XMLPARSE(CONTENT T.ENAME || ','WELLFORMED) ORDER BY T.ENAME).GETCLOBVAL(),',')  AS NAMES   FROM SCOTT.EMP T   WHERE T.DEPTNO=20  GROUP BY T.DEPTNO;

效果：

文章来源: https://blog.csdn.net/makai5521/article/details/90709712