oracle - 如何使用 PL/SQL 查找序列是否存在

Question

我需要使用 PL/SQL 查找是否有名为例如的特定序列MY_SEQ 退出。如果序列存在，则删除它并创建一个新序列，否则只创建一个新序列。

E.G. (伪代码)

IF EXISTS(MY_SEQ) THEN
BEGIN
   DROP SEQUENCE MY_SEQ;
   CREATE SEQUENCE MY_SEQ...
END;
ELSE
BEGIN
  CREATE SEQUENCE MY_SEQ;
END;

Answer 1

您可以检查字典 View ALL_SEQUENCES(如果执行用户是所有者，则检查USER_SEQUENCES)，例如:

BEGIN
   FOR cc IN (SELECT sequence_name as sequence_exists
                FROM all_sequences
               WHERE sequence_owner = :seq_owner
                 AND sequence_name = :seq_name) LOOP
      -- sequence exists, drop it (at most there will be *one* sequence)
      EXECUTE IMMEDIATE 'DROP SEQUENCE XXX';
   END LOOP;
   -- create sequence
   EXECUTE IMMEDIATE 'CREATE SEQUENCE XXX';
END;