Question

我需要放一张桌子并换一张新桌子。如果我删除表并且该表不存在，则会出现错误

如何检查表格是否存在？

我正在研究Oracle 11g

提前致谢。

Answer 1

你可以这样做：

DECLARE v_exist PLS_INTEGER;
BEGIN

SELECT COUNT(*) INTO v_exist
FROM user_tables
WHERE table_name = 'YOURTABLEHERE';

IF v_exist = 1 THEN
    EXECUTE IMMEDIATE 'DROP TABLE YOURTABLEHERE';
END IF;

Answer 2

DECLARE
  eTABLE_OR_VIEW_DOES_NOT_EXIST  EXCEPTION;
  PRAGMA EXCEPTION_INIT(eTABLE_OR_VIEW_DOES_NOT_EXIST, -942);
BEGIN
  EXECUTE IMMEDIATE 'DROP TABLE SCHEMA.WHATEVER';
EXCEPTION
  WHEN eTABLE_OR_VIEW_DOES_NOT_EXIST THEN
    NULL;
END;

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Answer 3

类似

select count(*) from user_tables 
where table_name= :table name

或

select count(*) from dba_tables
where owner = :table owner
and table_name = :table name

或严厉的替代方案：

begin execute immediate 'drop table table_name'; 
exception when others then null; 
end;

Answer 4

我一直在使用以下程序来处理这个问题：

create or replace procedure drop_table_if_exists ( p_table_name varchar2 )
is
  it_exist number;
begin
  select count(*) 
     into it_exists
     from user_tables
     where table_name = p_table_name
  ;
  if it_exists >= 1 then
    execute immediate 'drop table '||p_table_name;
  end if;
end;
/

exec drop_table_if_exists ( 'TABLE_TO_DROP' );

如果我删除一个表并且表不存在，我会收到错误

4 个答案: