sql - 启用 oracle 约束的问题

Question

几天来，我一直在尝试禁用所有表的约束、插入数据并启用约束。它有效，但我做了一些测试，当我插入一个不尊重外键的行时，启用约束时没有错误消息。我只能看到该约束未经过验证。

这是禁用的代码

begin    
     BEGIN
      FOR rec IN ( SELECT constraint_name, table_name FROM user_constraints WHERE  constraint_type = 'R' OR constraint_type = 'P' )
      LOOP
        BEGIN
        EXECUTE IMMEDIATE 'alter table '||rec.table_name||' disable constraint '||rec.constraint_name;
         EXCEPTION WHEN OTHERS THEN
             dbms_output.put_line( 'ERROR: alter table '||rec.table_name||' DISABLE constraint '||rec.constraint_name||';' );
        END;      
      END LOOP;
      DBMS_OUTPUT.PUT_LINE('CONSTRAINTS DISABLED');
     END;
     BEGIN
     FOR rec IN ( SELECT trigger_name FROM user_triggers WHERE TRIGGER_NAME NOT LIKE 'BIN$%' )
      LOOP
            EXECUTE IMMEDIATE 'alter trigger '||rec.trigger_name||' disable';
      END LOOP;
    END;
    DBMS_OUTPUT.PUT_LINE('TRIGGERS DISABLED');
end;    
/

这是启用的代码

begin
  BEGIN
      FOR rec IN ( SELECT constraint_name, table_name FROM user_constraints where status = 'DISABLED' and constraint_type = 'R' OR constraint_type = 'P' )
      LOOP
        BEGIN
          EXECUTE IMMEDIATE 'alter table '||rec.table_name||' enable constraint '||rec.constraint_name;
          dbms_output.put_line('alter table '||rec.table_name||' enable constraint '||rec.constraint_name);
        EXCEPTION
          WHEN OTHERS THEN
            dbms_output.put_line('ERROR: alter table '||rec.table_name||' enable constraint '||rec.constraint_name||' ;' );

        END;
      END LOOP;
    END;
                DBMS_OUTPUT.PUT_LINE('CONSTRAINTS ENABLED');
    BEGIN
      FOR rec IN ( SELECT trigger_name FROM user_triggers WHERE TRIGGER_NAME NOT LIKE 'BIN$%' )
      LOOP
          EXECUTE IMMEDIATE 'alter trigger '||rec.trigger_name||' enable';
      END LOOP;
    END;
                DBMS_OUTPUT.PUT_LINE('TRIGGERS ENABLED');
END;

我不知道如何在最后检查所有约束并在它不起作用时进行回滚。

Answer 1

首先，您的代码会捕获无法启用约束时引发的错误，并且会丢弃该错误而不是重新引发它。这几乎总是一个错误。如果你不想忽略启用约束失败的事实，你会想要类似的东西

FOR rec IN ( SELECT constraint_name, 
                    table_name 
               FROM user_constraints 
              where status = 'DISABLED' 
                and constraint_type = 'R' 
                 OR constraint_type = 'P' )
LOOP
  BEGIN
    l_sql_stmt := 'alter table '||rec.table_name||
                  ' enable constraint ' || rec.constraint_name;
    dbms_output.put_line( l_sql_stmt );
    EXECUTE IMMEDIATE l_sql_stmt;
  EXCEPTION
    WHEN OTHERS THEN
      dbms_output.put_line('ERROR: ' || l_sql_stmt );
      raise; -- re-raise the exception
  END;
END LOOP;

因为 ALTER TABLE 是 DDL，所以不能回滚。如果您在启用一个约束时遇到错误，则无法回滚所有先前约束的启用。

根据您上次的更新，听起来您可能根本不想禁用和启用约束。您可能只想创建可延迟的约束。

SQL> create table foo (
  2    col1 number
  3  );

Table created.

SQL> ed
Wrote file afiedt.buf

  1  alter table foo
  2    add constraint pk_foo
  3        primary key( col1 )
  4*       deferrable
SQL> /

Table altered.

通常，这与任何其他主键约束一样

SQL> insert into foo values( 1 );

1 row created.

SQL> insert into foo values( 1 );
insert into foo values( 1 )
*
ERROR at line 1:
ORA-00001: unique constraint (SCOTT.PK_FOO) violated


SQL> rollback;

Rollback complete.

但如果您推迟约束，则在您提交之前不会对其进行验证。如果在事务结束时违反约束，事务将回滚。

SQL> alter session set constraints = deferred;

Session altered.

SQL> select * from foo;

no rows selected

SQL> insert into foo values( 1 );

1 row created.

SQL> insert into foo values( 1 );

1 row created.

SQL> insert into foo values( 1 );

1 row created.

SQL> commit;
commit
*
ERROR at line 1:
ORA-02091: transaction rolled back
ORA-00001: unique constraint (SCOTT.PK_FOO) violated