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  • Oracle函数之LISTAGG(按照字符连接字符串)

    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 ORDER BY 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。

     
     select listagg(ename,',')within group(order by sal)name    from emp;
    

    结果:

     
    NAME
    ----------------------------------------------------------------------------------------------------
    SMITH,JAMES,ADAMS,MARTIN,WARD,MILLER,TURNER,ALLEN,CLARK,BLAKE,JONES,FORD,SCOTT,KING

    +groupby分组函数:

     
     select deptno,listagg(ename,',')within group(order by sal)name from emp group by deptno;

    结果:

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

    +over(partition by )分析函数:

     
    select deptno,ename,sal,listagg(ename,',')within group(order by sal)over(partition by deptno)name from emp;

    结果:

     
    
        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 
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  • 原文地址:https://www.cnblogs.com/hzcya1995/p/13288747.html
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