Ala*_*orm 322 sql oracle sql-drop
我正在为Oracle数据库编写一些迁移脚本,并且希望Oracle有类似MySQL的IF EXISTS构造.
具体来说,每当我想在MySQL中删除表时,我都会这样做
DROP TABLE IF EXISTS `table_name`;
这样,如果表不存在,DROP则不会产生错误,脚本可以继续.
Oracle是否有类似的机制？我意识到我可以使用以下查询来检查表是否存在
SELECT * FROM dba_tables where table_name = 'table_name';
但是把它与a绑在一起的语法DROP正在逃避我.
Jef*_*emp 540
最好和最有效的方法是捕获"未找到表"异常:这避免了检查表是否存在两次的开销; 并且不会遇到这样的问题:如果DROP由于某些其他原因(可能很重要)而失败,则仍会向调用者提出异常:
BEGIN
EXECUTE IMMEDIATE 'DROP TABLE ' || table_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -942 THEN
RAISE;
END IF;
END;
ADDENDUM 作为参考,以下是其他对象类型的等效块:
序列
BEGIN
EXECUTE IMMEDIATE 'DROP SEQUENCE ' || sequence_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -2289 THEN
RAISE;
END IF;
END;
视图
BEGIN
EXECUTE IMMEDIATE 'DROP VIEW ' || view_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -942 THEN
RAISE;
END IF;
END;
触发
BEGIN
EXECUTE IMMEDIATE 'DROP TRIGGER ' || trigger_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -4080 THEN
RAISE;
END IF;
END;
指数
BEGIN
EXECUTE IMMEDIATE 'DROP INDEX ' || index_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -1418 THEN
RAISE;
END IF;
END;
柱
BEGIN
EXECUTE IMMEDIATE 'ALTER TABLE ' || table_name
|| ' DROP COLUMN ' || column_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -904 AND SQLCODE != -942 THEN
RAISE;
END IF;
END;
数据库链接
BEGIN
EXECUTE IMMEDIATE 'DROP DATABASE LINK ' || dblink_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -2024 THEN
RAISE;
END IF;
END;
物化视图
BEGIN
EXECUTE IMMEDIATE 'DROP MATERIALIZED VIEW ' || mview_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -12003 THEN
RAISE;
END IF;
END;
类型
BEGIN
EXECUTE IMMEDIATE 'DROP TYPE ' || type_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -4043 THEN
RAISE;
END IF;
END;
约束
BEGIN
EXECUTE IMMEDIATE 'ALTER TABLE ' || table_name
|| ' DROP CONSTRAINT ' || constraint_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -2443 AND SQLCODE != -942 THEN
RAISE;
END IF;
END;
调度程序作业
BEGIN
DBMS_SCHEDULER.drop_job(job_name);
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -27475 THEN
RAISE;
END IF;
END;
用户/架构
BEGIN
EXECUTE IMMEDIATE 'DROP USER ' || user_name;
/* you may or may not want to add CASCADE */
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -1918 THEN
RAISE;
END IF;
END;
包
BEGIN
EXECUTE IMMEDIATE 'DROP PACKAGE ' || package_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -4043 THEN
RAISE;
END IF;
END;
程序
BEGIN
EXECUTE IMMEDIATE 'DROP PROCEDURE ' || procedure_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -4043 THEN
RAISE;
END IF;
END;
功能
BEGIN
EXECUTE IMMEDIATE 'DROP FUNCTION ' || function_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -4043 THEN
RAISE;
END IF;
END;
表空间
BEGIN
EXECUTE IMMEDIATE 'DROP TABLESPACE' || tablespace_name;
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -959 THEN
RAISE;
END IF;
END;
Mar*_*urz 126
declare
c int;
begin
select count(*) into c from user_tables where table_name = upper('table_name');
if c = 1 then
execute immediate 'drop table table_name';
end if;
end;
这是用于检查当前模式中的表是否存在.要检查给定的表是否已存在于不同的模式中,您必须使用all_tables而不是user_tables添加条件all_tables.owner = upper('schema_name')
小智 25
我一直在寻找相同的但我最终写了一个程序来帮助我:
CREATE OR REPLACE PROCEDURE DelObject(ObjName varchar2,ObjType varchar2)
IS
v_counter number := 0;
begin
if ObjType = 'TABLE' then
select count(*) into v_counter from user_tables where table_name = upper(ObjName);
if v_counter > 0 then
execute immediate 'drop table ' || ObjName || ' cascade constraints';
end if;
end if;
if ObjType = 'PROCEDURE' then
select count(*) into v_counter from User_Objects where object_type = 'PROCEDURE' and OBJECT_NAME = upper(ObjName);
if v_counter > 0 then
execute immediate 'DROP PROCEDURE ' || ObjName;
end if;
end if;
if ObjType = 'FUNCTION' then
select count(*) into v_counter from User_Objects where object_type = 'FUNCTION' and OBJECT_NAME = upper(ObjName);
if v_counter > 0 then
execute immediate 'DROP FUNCTION ' || ObjName;
end if;
end if;
if ObjType = 'TRIGGER' then
select count(*) into v_counter from User_Triggers where TRIGGER_NAME = upper(ObjName);
if v_counter > 0 then
execute immediate 'DROP TRIGGER ' || ObjName;
end if;
end if;
if ObjType = 'VIEW' then
select count(*) into v_counter from User_Views where VIEW_NAME = upper(ObjName);
if v_counter > 0 then
execute immediate 'DROP VIEW ' || ObjName;
end if;
end if;
if ObjType = 'SEQUENCE' then
select count(*) into v_counter from user_sequences where sequence_name = upper(ObjName);
if v_counter > 0 then
execute immediate 'DROP SEQUENCE ' || ObjName;
end if;
end if;
end;
希望这可以帮助
mis*_*kin 12
只是想发布一个完整的代码来创建一个表,如果已经存在使用Jeffrey的代码就放弃它(对他而言,不是我!).
BEGIN
BEGIN
EXECUTE IMMEDIATE 'DROP TABLE tablename';
EXCEPTION
WHEN OTHERS THEN
IF SQLCODE != -942 THEN
RAISE;
END IF;
END;
EXECUTE IMMEDIATE 'CREATE TABLE tablename AS SELECT * FROM sourcetable WHERE 1=0';
END;
使用SQL*PLUS,您还可以使用WHENEVER SQLERROR命令:
WHENEVER SQLERROR CONTINUE NONE
DROP TABLE TABLE_NAME;
WHENEVER SQLERROR EXIT SQL.SQLCODE
DROP TABLE TABLE_NAME;
随着CONTINUE NONE报告错误,但脚本会继续.在EXIT SQL.SQLCODE出现错误的情况下脚本将被终止.
另一种方法是定义一个异常，然后只捕获该异常，让所有其他异常传播。
Declare
eTableDoesNotExist Exception;
PRAGMA EXCEPTION_INIT(eTableDoesNotExist, -942);
Begin
EXECUTE IMMEDIATE ('DROP TABLE myschema.mytable');
Exception
When eTableDoesNotExist Then
DBMS_Output.Put_Line('Table already does not exist.');
End;
小智 5
我更喜欢以下经济解决方案
BEGIN
FOR i IN (SELECT NULL FROM USER_OBJECTS WHERE OBJECT_TYPE = 'TABLE' AND OBJECT_NAME = 'TABLE_NAME') LOOP
EXECUTE IMMEDIATE 'DROP TABLE TABLE_NAME';
END LOOP;
END;