检查架构中的IF表EXISTS时出现Oracle PL / SQL过程错误[重复]

这个问题在这里已有答案：

• DDL statements in PL/SQL? 2个答案

我正在使用SQL Developer Tool创建一个过程来检查是否存在名为TRANSPORT_PRODUCT的表，如果它存在，则截断它，如果它不创建它 .

场景1：当schema_PRODUCT在架构中不存在并且我编译过程时，编译过程时出现以下错误

Error(44,2): PL/SQL: SQL Statement ignored
Error(44,14): PL/SQL: ORA-00942: table or view does not exist

场景2：如果我创建表TRANSPORT_PRODUCT然后创建过程并运行，一切看起来都很好，除了我在过程中使用以下查询来检查表是否存在，其中变量TABLE_EXISTS初始化为0，

select  COUNT(*) INTO   TABLE_EXISTS from    user_tables where   table_name= TABLE_NAME;
DBMS_OUTPUT.PUT_LINE('IF 0 THEN TABLE DOES NOT EXISTS ELSE TABLE EXISTS -'||TO_CHAR(TABLE_EXISTS,99));

一个值48存储在TABLE_EXISTS ..这对我来说很奇怪:(

场景3：如果我创建TRANSPORT_PRODUCT表然后创建过程，删除TRANSPORT_PRODUCT并运行该过程，我得到以下消息，我不知道为什么该过程依赖于表！

Error report:
ORA-06550: line 1, column 7:
PLS-00905: object XAAL5.EXPORT_PRODUCT is invalid
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored
06550. 00000 -  "line %s, column %s:\n%s"
*Cause:    Usually a PL/SQL compilation error.
*Action:

我的程序：

CREATE OR REPLACE PROCEDURE EXPORT_PRODUCT IS
        TABLE_NAME      VARCHAR2(50) NULL;
        TABLE_EXISTS    INTEGER:=0;
        TRUNC_TABLE     VARCHAR2(50) NULL;
        CREATE_TABLE    VARCHAR2(1000) NULL;
    BEGIN
        DBMS_OUTPUT.PUT_LINE('Procedure Start Time :' || to_char(systimestamp,'DD-MM-YY HH:MM:SS'));

        TABLE_NAME:='TRANSPORT_PRODUCT';

        select  COUNT(*) INTO   TABLE_EXISTS from    user_tables where   table_name= TABLE_NAME;

        DBMS_OUTPUT.PUT_LINE('IF 0 THEN TABLE DOES NOT EXISTS ELSE TABLE EXISTS -'||TO_CHAR(TABLE_EXISTS,99));

        IF (TABLE_EXISTS<>0) THEN
            BEGIN
                DBMS_OUTPUT.PUT_LINE(TABLE_NAME||' TRANSPORT_PRODUCT TABLE EXISTS AND WILL BE TRUNCATED');
                TRUNC_TABLE:='truncate table '|| TABLE_NAME;
                --DBMS_OUTPUT.PUT_LINE(TRUNC_TABLE);
                execute immediate TRUNC_TABLE;
            END;
        ELSE
            BEGIN 
                DBMS_OUTPUT.PUT_LINE(TABLE_NAME ||' DOES NOT EXISTS AND WILL BE CREATED');
                CREATE_TABLE:=
                    'CREATE TABLE TRANSPORT_PRODUCT (
                        ROW_NUMBER      NUMBER,             
                        PRODUCTID       VARCHAR2(20), 
                        PRODUCTNAME     VARCHAR2(100), 
                        OWNER           VARCHAR2(20), 
                        DIVISIONID      VARCHAR2(20), 
                        MERCHLEVEL1     VARCHAR2(20), 
                        MERCHLEVEL2     VARCHAR2(20), 
                        MERCHLEVEL3     VARCHAR2(20), 
                        MERCHLEVEL4     VARCHAR2(20), 
                        STREAMID        VARCHAR2(20), 
                        SPECIFICATION   VARCHAR2(20), 
                        SSS             VARCHAR2(20))';
                execute immediate CREATE_TABLE;
            END;
        END IF;

     -- INSERT PRODUCT INTO TRANSPORT_PRODUCT
        INSERT INTO TRANSPORT_PRODUCT (ROW_NUMBER,PRODUCTID,PRODUCTNAME,OWNER, DIVISIONID,MERCHLEVEL1, MERCHLEVEL2, MERCHLEVEL3,MERCHLEVEL4,STREAMID,SPECIFICATION,SSS) 
        SELECT  ROWNUM,
                PRODUCTID,
                PRODUCTNAME,
                OWNER,
                DIVISIONID,
                MERCHLEVEL1,
                MERCHLEVEL2,
                MERCHLEVEL3,
                MERCHLEVEL4,
                STREAMID,
                SPECIFICATION,
                SSS
        FROM PRODUCT; 

        DBMS_OUTPUT.PUT_LINE('Procedure End Time :' || to_char(systimestamp,'DD-MM-YY HH:MM:SS'));

   exec buildfile('select * from TRANSPORT_PRODUCT where rownum<=500');

      commit;   
    END;