Question

我在Oracle中遇到此错误：

ORA-00933：SQL命令未正确结束
  对于
  DROP SEQUENCE IF EXISTS ownername.seq_name;

为什么我会看到这个？

Answer 1

Oracle中的DROP SEQUENCE命令中不存在IF EXISTS子句。

您可以使用PLSQL块来忽略错误：

SQL> DECLARE
  2     sequence_doesnt_exist EXCEPTION;
  3     PRAGMA EXCEPTION_INIT(sequence_doesnt_exist, -2289);
  4  BEGIN
  5     EXECUTE IMMEDIATE 'DROP SEQUENCE seq_name';
  6  EXCEPTION
  7     WHEN sequence_doesnt_exist THEN NULL;
  8  END;
  9  /

PL/SQL procedure successfully completed

Answer 2

正如其他人所提到的，IF EXISTS不适用于DROP SEQUENCE命令。

要测试序列是否存在，您需要检查相应的视图：

USER_SEQUENCES

SELECT * 
  FROM USER_SEQUENCES
 WHERE sequence_name = ?

DBA_SEQUENCES

SELECT * 
  FROM DBA_SEQUENCES
 WHERE sequence_name = ?

ALL_SEQUENCES

SELECT * 
  FROM ALL_SEQUENCES
 WHERE sequence_name = ?

示例：

BEGIN
   FOR i IN (SELECT sequence_name 
               FROM USER_SEQUENCES
              WHERE sequence_name = ?) 
   LOOP
     EXECUTE IMMEDIATE ('DROP SEQUENCE '|| i.sequence_name);
   END LOOP;
END;

Answer 3

问题是“if exists”在Oracle中不起作用。使用：

drop sequence ownername.seq_name;

Answer 4

试试这个：

DECLARE
 iNum NUMBER DEFAULT 0;
BEGIN
  SELECT COUNT(1) 
      INTO  iNum 
   FROM ALL_SEQUENCES 
  WHERE SEQUENCE_OWNER='<OWNER_NAME>' 
       AND SEQUENCE_NAME = '<YOUR_SEQUENCE_NAME>';
 IF  iNum> 0 THEN
     EXECUTE IMMEDIATE 'DROP SEQUENCE <OWNER_NAME>.<YOUR_SEQUENCE_NAME>';
 END IF;
END;

ORA-00933：SQL命令未正确结束

4 个答案: