LISTAGG Oracle function of

Recently in the learning process, I found a very interesting function, which can be realized splicing column values. Let us look at the specific usage.

usage:

Its role, the official interpretation of the document are as follows:

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.

I.e., within each group, LISTAGG column explants are ordered according to the order by clause, the results sorted spliced together.

measure_expr: it can be any expression-based column.

delimiter: delimiter, default NUL

order_by_clause: order by clause determines the order of column values are spliced.

By this use, it can be seen not only as a function of LISTAGG ordinary function, can also be used as analytical functions.

Usage order_by_clause and query_partition_clause as follows:

The following Examples illustrate the function:

Ordinary function, sort of wages, spliced with a comma.

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

Group function:

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

Analysis functions:

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.