lightdb22.3预览-listagg 增强

lightdb22.3 - listagg 增强

LightDB 在22.3版本对listagg 进行了增强，现在支持同时使用within group(order by xxx ) 和over(partition by xxx)

oracle listagg

oracle 19c 中listagg 语法如下用法：

DISTINCT 从19c 开始支持

LightDB listagg

之前版本限制：

1. 不支持 WITHIN GROUP order_by_clause 与 OVER query_partition_clause一起用。

2. 不支持DISTINCT 与 OVER query_partition_clause一起使用

22.3 版本取出来上述1的限制，目前只有如下限制：

• 不支持DISTINCT 与 WITHIN GROUP order_by_clause OVER query_partition_clause 一起使用，其实就是上述的2

案例

表结构及数据：

CREATE TABLE EMP
(   EMPNO    NUMBER(4, 0),
    ENAME    VARCHAR2(10),
    JOB      VARCHAR2(9),
    MGR      NUMBER(4, 0),
    HIREDATE DATE,
    SAL      NUMBER(7, 2),
    COMM     NUMBER(7, 2),
    DEPTNO   NUMBER(2, 0),
    DNAME    VARCHAR2(100),
    CONSTRAINT PK_EMP PRIMARY KEY (EMPNO)
);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7369, 'SMITH',  'CLERK',    7902, to_date('1980-12-17','yyyy-mm-dd'), 800.00,  null,    20, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7499, 'ALLEN',  'SALESMAN', 7698, to_date('1981-02-20','yyyy-mm-dd'), 1600.00, 300.00,  30, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7521, 'WARD',   'SALESMAN', 7698, to_date('1981-02-22','yyyy-mm-dd'), 1250.00, 500.00,  30, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7566, 'JONES',  'MANAGER',  7839, to_date('1981-04-02','yyyy-mm-dd'), 2975.00, null,    20, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7654, 'MARTIN', 'SALESMAN', 7698, to_date('1981-09-28','yyyy-mm-dd'), 1250.00, 1400.00, 30, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7698, 'BLAKE',  'MANAGER',  7839, to_date('1981-05-01','yyyy-mm-dd'), 2850.00, null,    30, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7782, 'CLARK',  'MANAGER',  7839, to_date('1981-06-09','yyyy-mm-dd'), 2450.00, null,    10, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7788, 'SCOTT',  'ANALYST',  7566, to_date('1987-04-19','yyyy-mm-dd'), 3000.00, null,    20, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7839, 'KING',   'PRESIDENT',null, to_date('1981-11-17','yyyy-mm-dd'), 5000.00, null,    10, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7844, 'TURNER', 'SALESMAN', 7698, to_date('1981-09-08','yyyy-mm-dd'), 1500.00, 0.00,    30, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7876, 'ADAMS',  'CLERK',    7788, to_date('1987-05-23','yyyy-mm-dd'), 1100.00, null,    20, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7900, 'JAMES',  'CLERK',    7698, to_date('1981-12-03','yyyy-mm-dd'), 950.00,  null,    30, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7902, 'FORD',   'ANALYST',  7566, to_date('1981-12-03','yyyy-mm-dd'), 3000.00, null,    20, null);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO, DNAME) values (7934, 'MILLER', 'CLERK',    7782, to_date('1982-01-23','yyyy-mm-dd'), 1300.00, null,    10, null);

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查询：

select listagg(ename, ',') within group(order by ename) over(partition by deptno) as enames,
       deptno,
       ename
  from EMP;
  
                  enames                | deptno | ename  
--------------------------------------+--------+--------
 CLARK,KING,MILLER                    |     10 | CLARK
 CLARK,KING,MILLER                    |     10 | KING
 CLARK,KING,MILLER                    |     10 | MILLER
 ADAMS,FORD,JONES,SCOTT,SMITH         |     20 | ADAMS
 ADAMS,FORD,JONES,SCOTT,SMITH         |     20 | FORD
 ADAMS,FORD,JONES,SCOTT,SMITH         |     20 | JONES
 ADAMS,FORD,JONES,SCOTT,SMITH         |     20 | SCOTT
 ADAMS,FORD,JONES,SCOTT,SMITH         |     20 | SMITH
 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD |     30 | ALLEN
 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD |     30 | BLAKE
 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD |     30 | JAMES
 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD |     30 | MARTIN
 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD |     30 | TURNER
 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD |     30 | WARD
(14 rows)

  
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不支持distinct:

chuhx@test=# select listagg(distinct ename, ',') within group(order by ename) over(partition by deptno) as enames, deptno, ename from EMP;
ERROR:  DISTINCT is not implemented for window functions
LINE 1: select listagg(distinct ename, ',') within group(order by en...

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参考

oracle LISTAGG