oracle函數listagg使用

作用

可以實現將多列記錄聚合為一列記錄，實現數據的壓縮

語法結構

listagg(measure_expr，delimiter) within group ( order by order_by_clause);

解釋：measure_expr可以是基於任何列的表達式

　　delimiter分隔符，默認為NULL

　　order_by_clause決定了列值的拼接順序

舉例

普通函數，對工資進行排序，並按照逗號進行拼接

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

分組函數

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

分析函數

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.