Oracle SQL Developer是Oracle近几年来推出的一款免费的图形界面SQL PL/SQL开发工具，在11g中它甚至被集成到了Oracle server软件中；如果你平常有用这款IDE的话，大概会注意到它提供了十分实用的Database copy,diff,export功能。

当在Oracle SQL developer中使用sys用户登录数据库，并尝试导出某些schema的ddl定义时，可能会丢失一些constraint约束的ddl信息，如以下例子:

我们尝试导出scott用户的表，索引以及约束的相关ddl，当使用sys用户登录数据库时，Oracle SQL developer给出的SQL:

--------------------------------------------------------
--  File created - Monday-August-30-2010
--------------------------------------------------------
--------------------------------------------------------
--  DDL for Table BONUS
--------------------------------------------------------

  CREATE TABLE "BONUS"
   (	"ENAME" VARCHAR2(10),
	"JOB" VARCHAR2(9),
	"SAL" NUMBER,
	"COMM" NUMBER
   ) ;
--------------------------------------------------------
--  DDL for Table DEPT
--------------------------------------------------------

  CREATE TABLE "DEPT"
   (	"DEPTNO" NUMBER(2,0),
	"DNAME" VARCHAR2(14),
	"LOC" VARCHAR2(13)
   ) ;
--------------------------------------------------------
--  DDL for Table EMP
--------------------------------------------------------

  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)
   ) ;
--------------------------------------------------------
--  DDL for Table SALGRADE
--------------------------------------------------------

  CREATE TABLE "SALGRADE"
   (	"GRADE" NUMBER,
	"LOSAL" NUMBER,
	"HISAL" NUMBER
   ) ;

--------------------------------------------------------
--  DDL for Index PK_DEPT
--------------------------------------------------------

  CREATE UNIQUE INDEX "PK_DEPT" ON "DEPT" ("DEPTNO")   ;
--------------------------------------------------------
--  DDL for Index PK_EMP
--------------------------------------------------------

  CREATE UNIQUE INDEX "PK_EMP" ON "EMP" ("EMPNO")   ;

以上SQL中未给出PK和FK约束的ddl信息。

如果使用scott用户登录数据库，导出自身schema的table,index,constraint定义信息时:

--------------------------------------------------------
--  File created - Monday-August-30-2010
--------------------------------------------------------
--------------------------------------------------------
--  DDL for Table BONUS
--------------------------------------------------------

  CREATE TABLE "BONUS"
   (	"ENAME" VARCHAR2(10),
	"JOB" VARCHAR2(9),
	"SAL" NUMBER,
	"COMM" NUMBER
   ) ;
--------------------------------------------------------
--  DDL for Table DEPT
--------------------------------------------------------

  CREATE TABLE "DEPT"
   (	"DEPTNO" NUMBER(2,0),
	"DNAME" VARCHAR2(14),
	"LOC" VARCHAR2(13)
   ) ;
--------------------------------------------------------
--  DDL for Table EMP
--------------------------------------------------------

  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)
   ) ;
--------------------------------------------------------
--  DDL for Table SALGRADE
--------------------------------------------------------

  CREATE TABLE "SALGRADE"
   (	"GRADE" NUMBER,
	"LOSAL" NUMBER,
	"HISAL" NUMBER
   ) ;

--------------------------------------------------------
--  Constraints for Table EMP
--------------------------------------------------------

  ALTER TABLE "EMP" ADD CONSTRAINT "PK_EMP" PRIMARY KEY ("EMPNO") ENABLE;

--------------------------------------------------------
--  Constraints for Table DEPT
--------------------------------------------------------

  ALTER TABLE "DEPT" ADD CONSTRAINT "PK_DEPT" PRIMARY KEY ("DEPTNO") ENABLE;
--------------------------------------------------------
--  DDL for Index PK_EMP
--------------------------------------------------------

  CREATE UNIQUE INDEX "PK_EMP" ON "EMP" ("EMPNO")   ;
--------------------------------------------------------
--  DDL for Index PK_DEPT
--------------------------------------------------------

  CREATE UNIQUE INDEX "PK_DEPT" ON "DEPT" ("DEPTNO")  ;

--------------------------------------------------------
--  Ref Constraints for Table EMP
--------------------------------------------------------

  ALTER TABLE "EMP" ADD CONSTRAINT "FK_DEPTNO" FOREIGN KEY ("DEPTNO")
	  REFERENCES "DEPT" ("DEPTNO") ENABLE;

Oracle SQL developer给出了正确的SQL，包含FK和PK约束。
这个Bug在8月(2010 Aug)被确认将影响此前所有版本的Oracle SQL developer。