作用
可以实现将多列记录聚合为一列记录，实现数据的压缩
语法结构
listagg(measure_expr，delimiter) within group ( order by order_by_clause);
解释：measure_expr可以是基于任何列的表达式
delimiter分隔符，默认为NULL
order_by_clause决定了列值的拼接顺序
举例
普通函数，对工资进行排序，并按照逗号进行拼接
1 SQL> select listagg(ename,',')within group(order by sal)name from emp; 2 3 NAME 4 ---------------------------------------------------------------------------------------------------- 5 SMITH,JAMES,ADAMS,MARTIN,WARD,MILLER,TURNER,ALLEN,CLARK,BLAKE,JONES,FORD,SCOTT,KING
分组函数
1 SQL> select deptno,listagg(ename,',')within group(order by sal)name from emp group by deptno; 2 3 DEPTNO NAME 4 ---------- ---------------------------------------------------------------------------------------------------- 5 10 MILLER,CLARK,KING 6 20 SMITH,ADAMS,JONES,FORD,SCOTT 7 30 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE
分析函数
1 SQL> select deptno,ename,sal,listagg(ename,',')within group(order by sal)over(partition by deptno)name from emp; 2 3 DEPTNO ENAME SAL NAME 4 ---------- ---------- ---------- ---------------------------------------- 5 10 MILLER 1300 MILLER,CLARK,KING 6 10 CLARK 2450 MILLER,CLARK,KING 7 10 KING 5000 MILLER,CLARK,KING 8 20 SMITH 800 SMITH,ADAMS,JONES,SCOTT,FORD 9 20 ADAMS 1100 SMITH,ADAMS,JONES,SCOTT,FORD 10 20 JONES 2975 SMITH,ADAMS,JONES,SCOTT,FORD 11 20 SCOTT 3000 SMITH,ADAMS,JONES,SCOTT,FORD 12 20 FORD 3000 SMITH,ADAMS,JONES,SCOTT,FORD 13 30 JAMES 950 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE 14 30 MARTIN 1250 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE 15 30 WARD 1250 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE 16 30 TURNER 1500 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE 17 30 ALLEN 1600 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE 18 30 BLAKE 2850 JAMES,MARTIN,WARD,TURNER,ALLEN,BLAKE 19 20 14 rows selected.