我有一个包含部门 ID、员工姓名和加入日期的表格。我想获取在给定部门的给定日期加入的所有员工的列表。
wm_concat
不管用。
试试wmsys.wm_concat
(10g+) 或listagg
(11g+)
尝试sys.STRAGG
SELECT department_id,
hire_date,
TRIM(TRAILING ',' FROM sys.STRAGG(last_name || ',')) names
FROM employees
GROUP BY department_id, hire_date
请参阅字符串聚合技术页面。
对于 9i,您可以在引用的页面中声明 UDAG 函数:
CREATE OR REPLACE TYPE t_string_agg AS OBJECT
(
g_string VARCHAR2(32767),
STATIC FUNCTION ODCIAggregateInitialize(sctx IN OUT t_string_agg)
RETURN NUMBER,
MEMBER FUNCTION ODCIAggregateIterate(self IN OUT t_string_agg,
value IN VARCHAR2 )
RETURN NUMBER,
MEMBER FUNCTION ODCIAggregateTerminate(self IN t_string_agg,
returnValue OUT VARCHAR2,
flags IN NUMBER)
RETURN NUMBER,
MEMBER FUNCTION ODCIAggregateMerge(self IN OUT t_string_agg,
ctx2 IN t_string_agg)
RETURN NUMBER
);
/
CREATE OR REPLACE TYPE BODY t_string_agg IS
STATIC FUNCTION ODCIAggregateInitialize(sctx IN OUT t_string_agg)
RETURN NUMBER IS
BEGIN
sctx := t_string_agg(NULL);
RETURN ODCIConst.Success;
END;
MEMBER FUNCTION ODCIAggregateIterate(self IN OUT t_string_agg,
value IN VARCHAR2 )
RETURN NUMBER IS
BEGIN
SELF.g_string := self.g_string || ',' || value;
RETURN ODCIConst.Success;
END;
MEMBER FUNCTION ODCIAggregateTerminate(self IN t_string_agg,
returnValue OUT VARCHAR2,
flags IN NUMBER)
RETURN NUMBER IS
BEGIN
returnValue := RTRIM(LTRIM(SELF.g_string, ','), ',');
RETURN ODCIConst.Success;
END;
MEMBER FUNCTION ODCIAggregateMerge(self IN OUT t_string_agg,
ctx2 IN t_string_agg)
RETURN NUMBER IS
BEGIN
SELF.g_string := SELF.g_string || ',' || ctx2.g_string;
RETURN ODCIConst.Success;
END;
END;
/
CREATE OR REPLACE FUNCTION string_agg (p_input VARCHAR2)
RETURN VARCHAR2
PARALLEL_ENABLE AGGREGATE USING t_string_agg;
/
使用它就像:
SELECT deptno, string_agg(ename) AS employees
FROM emp
GROUP BY deptno;
您也可以尝试this question中的方法(如果您有大桌子,这会很慢)
看这里:http ://www.oracle-base.com/articles/misc/string-aggregation-techniques.php
在该页面上查找 Oracle 9i 中 ROW_NUMBER() 和 SYS_CONNECT_BY_PATH 函数的示例。
如果 PL/SQL 是一个选项,那么 TABLE_TO_COMMA 过程可能会起作用:http ://docs.oracle.com/cd/E11882_01/appdev.112/e25788/d_util.htm#ARPLS73271
首先,不要使用,WM_CONCAT
因为它是一个未记录的功能,并且已从最新的12c 版本中删除。任何一直依赖wm_concat
功能的应用程序一旦升级到12c
. 请参阅为什么不在 Oracle 中使用 WM_CONCAT 函数?
SQL> select banner from v$version where rownum = 1;
BANNER
----------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production
SQL> SELECT object_name
2 FROM dba_objects
3 WHERE owner='WMSYS'
4 AND object_name LIKE 'WM\_%' ESCAPE '\';
OBJECT_NAME
----------------------------------------------------------------------------
WM_REPLICATION_INFO
WM_RDIFF
WM_PERIOD
WM_PERIOD
WM_OVERLAPS
WM_MEETS
WM_LESSTHAN
WM_LDIFF
WM_INTERSECTION
WM_INSTALLATION
WM_GREATERTHAN
WM_EVENTS_INFO
WM_ERROR
WM_ERROR
WM_EQUALS
WM_DDL_UTIL
WM_DDL_UTIL
WM_CONTAINS
WM_COMPRESS_BATCH_SIZES
WM_COMPRESSIBLE_TABLES
20 rows selected.
您将收到“<strong>invalid identifier”错误:
SQL> SELECT banner FROM v$version;
BANNER
----------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production
PL/SQL Release 12.1.0.1.0 - Production
CORE 12.1.0.1.0 Production
TNS for 64-bit Windows: Version 12.1.0.1.0 - Production
NLSRTL Version 12.1.0.1.0 - Production
SQL> SELECT deptno, wm_concat(ename) FROM emp;
SELECT deptno, wm_concat(ename) FROM emp
*
ERROR at line 1:
ORA-00904: "WM_CONCAT": invalid identifier
因此,没有必要依赖最新版本中不再提供的未记录功能。
有多种字符串聚合技术:
例如,
SELECT deptno, LISTAGG(ename, ',') WITHIN GROUP (ORDER BY ename) AS employees
FROM emp
GROUP BY deptno;
DEPTNO EMPLOYEES
---------- --------------------------------------------------
10 CLARK,KING,MILLER
20 ADAMS,FORD,JONES,SCOTT,SMITH
30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD
3 rows selected.
例如,
SELECT deptno,
LTRIM(MAX(SYS_CONNECT_BY_PATH(ename,','))
KEEP (DENSE_RANK LAST ORDER BY curr),',') AS employees
FROM (SELECT deptno,
ename,
ROW_NUMBER() OVER (PARTITION BY deptno ORDER BY ename) AS curr,
ROW_NUMBER() OVER (PARTITION BY deptno ORDER BY ename) -1 AS prev
FROM emp)
GROUP BY deptno
CONNECT BY prev = PRIOR curr AND deptno = PRIOR deptno
START WITH curr = 1;
DEPTNO EMPLOYEES
---------- --------------------------------------------------
10 CLARK,KING,MILLER
20 ADAMS,FORD,JONES,SCOTT,SMITH
30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD
3 rows selected.
Tim Hall 的几个很好的例子。