最近在学习的过程中,发现一个挺有意思的函数,它可实现对列值的拼接。下面我们来看看其具体用法。
用法:
对其作用,官方文档的解释如下:
For a specified measure, LISTAGG orders data within each group specified in the ORDERBY clause and then concatenates the values of the measure column.
即在每个分组内,LISTAGG根据order by子句对列植进行排序,将排序后的结果拼接起来。
measure_expr:可以是任何基于列的表达式。
delimiter:分隔符,默认为NUL
order_by_clause:order by子句决定了列值被拼接的顺序。
通过该用法,可以看出LISTAGG函数不仅可作为一个普通函数使用,也可作为分析函数。
order_by_clause和query_partition_clause的用法如下:
下面对该函数进行举例说明:
普通函数,对工资进行排序,用逗号进行拼接。
SQL> select listagg(ename,',')within group(order by sal)name from emp;
NAME
----------------------------------------------------------------------------------------------------
SMITH,JAMES,ADAMS,MARTIN,WARD,MILLER,TURNER,ALLEN,CLARK,BLAKE,JONES,FORD,SCOTT,KING
分组函数:
SQL> select deptno,listagg(ename,',')within group(order by sal)name from emp group by deptno;
DEPTNO NAME
--------------------------------------------------------------------------------------------------------------
10 MILLER,CLARK,KING
20 SMITH,ADAMS,JONES,FORD,SCOTT
30 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE
分析函数:
SQL> select deptno,ename,sal,listagg(ename,',')within group(order by sal)over(partition by deptno)name from emp;
DEPTNO ENAME SAL NAME
---------- ---------- ---------- ----------------------------------------
10 MILLER 1300 MILLER,CLARK,KING
10 CLARK 2450 MILLER,CLARK,KING
10 KING 5000 MILLER,CLARK,KING
20 SMITH 800 SMITH,ADAMS,JONES,SCOTT,FORD
20 ADAMS 1100 SMITH,ADAMS,JONES,SCOTT,FORD
20 JONES 2975 SMITH,ADAMS,JONES,SCOTT,FORD
20 SCOTT 3000 SMITH,ADAMS,JONES,SCOTT,FORD
20 FORD 3000 SMITH,ADAMS,JONES,SCOTT,FORD
30 JAMES 950 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE
30 MARTIN 1250 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE
30 WARD 1250 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE
30 TURNER 1500 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE
30 ALLEN 1600 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE
30 BLAKE 2850 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE
14 rows selected.
该贴被xpisme编辑于2015-7-20 23:17:03