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  • wmsys.wm_concat的几个用法

    今天才发现了wmsys.wm_concat这个有趣有用的函数,它的作用是以','链接字符。

    例子如下:

    SQL> create table idtable (id number,name varchar2(30));

    Table created

    SQL> insert into idtable values(10,'ab');

    1 row inserted

    SQL> insert into idtable values(10,'bc');

    1 row inserted

    SQL> insert into idtable values(10,'cd');

    1 row inserted

    SQL> insert into idtable values(20,'hi');

    1 row inserted

    SQL> insert into idtable values(20,'ij');

    1 row inserted
    SQL> insert into idtable values(20,'mn');

    1 row inserted

    SQL> select * from idtable;

            ID NAME
    ---------- ------------------------------
            10 ab
            10 bc
            10 cd
            20 hi
            20 ij
            20 mn

    6 rows selected
    SQL> select id,wmsys.wm_concat(name) name from idtable
      2  group by id;

            ID NAME
    ---------- --------------------------------------------------------------------------------
            10 ab,bc,cd
            20 hi,ij,mn

    SQL> select id,wmsys.wm_concat(name) over (order by id) name from idtable;

            ID NAME
    ---------- --------------------------------------------------------------------------------
            10 ab,bc,cd
            10 ab,bc,cd
            10 ab,bc,cd
            20 ab,bc,cd,hi,ij,mn
            20 ab,bc,cd,hi,ij,mn
            20 ab,bc,cd,hi,ij,mn

    6 rows selected

    SQL> select id,wmsys.wm_concat(name) over (order by id,name) name from idtable;

            ID NAME
    ---------- --------------------------------------------------------------------------------
            10 ab
            10 ab,bc
            10 ab,bc,cd
            20 ab,bc,cd,hi
            20 ab,bc,cd,hi,ij
            20 ab,bc,cd,hi,ij,mn

    6 rows selected

    个人觉得这个用法比较有趣.

    SQL> select id,wmsys.wm_concat(name) over (partition by id) name from idtable;

            ID NAME
    ---------- --------------------------------------------------------------------------------
            10 ab,bc,cd
            10 ab,bc,cd
            10 ab,bc,cd
            20 hi,ij,mn
            20 hi,ij,mn
            20 hi,ij,mn

    6 rows selected

    SQL> select id,wmsys.wm_concat(name) over (partition by id,name) name from idtable;

            ID NAME
    ---------- --------------------------------------------------------------------------------
            10 ab
            10 bc
            10 cd
            20 hi
            20 ij
            20 mn

    6 rows selected

    本文来自CSDN博客,转载请标明出处:http://blog.csdn.net/YY_MM_DD/archive/2008/10/30/3182953.aspx

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  • 原文地址:https://www.cnblogs.com/sumsen/p/2525786.html
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