甲骨文SYS_CONNECT_BY_PATH击中4000字符的限制

Question

我想运行类似下面针对从Java的Oracle 9i数据库的查询（一个例子的表结构和示例性数据是下文）。

 
SELECT deptno 
,  SUBSTR(comma_list, 2) comma_list 
FROM (SELECT deptno 
     ,  SYS_CONNECT_BY_PATH(ename, ',') comma_list 
     ,  row_number 
     ,  row_count 
     FROM (SELECT deptno 
       ,  ename 
       ,  ROW_NUMBER()OVER(PARTITION BY deptno 
             ORDER BY  empno) row_number 
       ,  COUNT(*)OVER(PARTITION BY deptno)  row_count 
       FROM wd_emp) 
     START WITH row_number = 1 
     CONNECT BY deptno = PRIOR deptno 
     AND  row_number = PRIOR row_number + 1) 
WHERE row_number = row_count; 

这工作正常。但是，如果它建立了comma_list的SYS_CONNECT_BY_PATH打VARCHAR2 4000个字符的限制，那么我得到一个“ORA-01489：字符串连接的结果是太长”错误。

有没有人对如何克服这种限制的任何建议，以便我可以串联超过4000个字符？

表和示例数据：

 

CREATE TABLE WD_DEPT(DEPTNO NUMBER(2) CONSTRAINT PK_DEPT PRIMARY KEY 
        ,DNAME VARCHAR2(14) 
        ,LOC VARCHAR2(13)); 

CREATE TABLE WD_EMP(EMPNO NUMBER(4) CONSTRAINT PK_EMP PRIMARY KEY 
        ,ENAME VARCHAR2(10) 
        ,JOB VARCHAR2(10) 
        ,MGR NUMBER(4) 
        ,HIREDATE DATE 
        ,SAL NUMBER(7,2) 
        ,DEPTNO NUMBER(2) CONSTRAINT FK_DEPTNO REFERENCES WD_DEPT); 

INSERT INTO WD_DEPT VALUES(10,'TEAM GREGORY','TABLE 3'); 
INSERT INTO WD_DEPT VALUES(20,'TEAM HANLEY','TABLE 2'); 
INSERT INTO WD_DEPT VALUES(30,'TEAM OFFIAH','TABLE 4'); 
INSERT INTO WD_DEPT VALUES(40,'TEAM BOTICA','TABLE 1'); 
INSERT INTO WD_DEPT VALUES(50,'TEAM SKERRETT','TABLE 4'); 
INSERT INTO WD_DEPT VALUES(60,'TEAM McGINTY','TABLE 1'); 
INSERT INTO WD_DEPT VALUES(70,'EMPTY TEAM','NO TABLE'); 

INSERT INTO WD_EMP VALUES(11,'GREGORY', 'TEAM LEAD', 28, to_date('18-JAN-2000', 'DD-MON-RRRR'), 800, 10); 
INSERT INTO WD_EMP VALUES(12,'BELL',  'DEVELOPER', 11, to_date('17-JAN-2000', 'DD-MON-RRRR'), 600, 10); 
INSERT INTO WD_EMP VALUES(13,'CLARKE', 'DEVELOPER', 11, to_date('16-JAN-2000', 'DD-MON-RRRR'), 600, 10); 
INSERT INTO WD_EMP VALUES(14,'HANLEY', 'TEAM LEAD', 28, to_date('15-JAN-2000', 'DD-MON-RRRR'), 800, 20); 
INSERT INTO WD_EMP VALUES(15,'BETTS', 'CONTRACTOR', 14, to_date('14-JAN-2000', 'DD-MON-RRRR'), 700, 20); 
INSERT INTO WD_EMP VALUES(16,'MILES', 'CONTRACTOR', 14, to_date('13-JAN-2000', 'DD-MON-RRRR'), 700, 20); 
INSERT INTO WD_EMP VALUES(17,'HAMPSON', 'DEVELOPER', 14, to_date('12-JAN-2000', 'DD-MON-RRRR'), 600, 20); 
INSERT INTO WD_EMP VALUES(18,'PRESTON', 'DEVELOPER', 14, to_date('11-JAN-2000', 'DD-MON-RRRR'), 600, 20); 
INSERT INTO WD_EMP VALUES(19,'OFFIAH', 'TEAM LEAD', 28, to_date('10-JAN-2000', 'DD-MON-RRRR'), 800, 30); 
INSERT INTO WD_EMP VALUES(20,'PLATT', 'DEVELOPER', 19, to_date('09-JAN-2000', 'DD-MON-RRRR'), 600, 30); 
INSERT INTO WD_EMP VALUES(21,'POTTER', 'DEVELOPER', 19, to_date('08-JAN-2000', 'DD-MON-RRRR'), 600, 30); 
INSERT INTO WD_EMP VALUES(22,'CASE',  'DEVELOPER', 19, to_date('07-JAN-2000', 'DD-MON-RRRR'), 600, 30); 
INSERT INTO WD_EMP VALUES(23,'BOTICA', 'TEAM LEAD', 28, to_date('06-JAN-2000', 'DD-MON-RRRR'), 800, 40); 
INSERT INTO WD_EMP VALUES(24,'GILL',  'DEVELOPER', 23, to_date('05-JAN-2000', 'DD-MON-RRRR'), 600, 40); 
INSERT INTO WD_EMP VALUES(25,'SKERRETT', 'TEAM LEAD', 28, to_date('04-JAN-2000', 'DD-MON-RRRR'), 800, 50); 
INSERT INTO WD_EMP VALUES(26,'McGINTY', 'TEAM LEAD', 28, to_date('03-JAN-2000', 'DD-MON-RRRR'), 800, 60); 
INSERT INTO WD_EMP VALUES(27,'LOWE',  'MANAGER', 28, to_date('02-JAN-2000', 'DD-MON-RRRR'), 900, NULL); 
INSERT INTO WD_EMP VALUES(28,'MONIE', 'MANAGER', NULL, to_date('01-JAN-2000', 'DD-MON-RRRR'), 1000, NULL); 

Answer 1

是否有必要建立逗号列表SQL？

因为你是从Java运行这个反正，也许你可以查询与“PARENT_ID”，“child_id”，“tree_level”列的行，并建立在应用程序代码的员工路径？我想，要拆分成一个列表反正现在（4000字符串不能直接显示的目的）。

Answer 2

两个想法：

• ，不要串联实际的字符串，但更短的占位符，并使用一些替代方法（在Java或其他方式）插入实名

• 您可以创建多个列：comma_list_，每个人拥有第400个员工的第n组。最终值将由客户端中的这些列形成。

Answer 3

我的理解是对VARCHAR2 4000个字符的限制是仅列 - 这VARCHAR2长度实际上是允许去大得多，例如在PL/SQL。你确定你的查询不是不正确地递归并生成一些大的笛卡尔积？