Question

我在程序包中有一个程序，我想实现一个逻辑，如果临时表有0行，它不会将临时表插入主表，然后转到程序包的下一个程序。

IF (not exists(select 1 from temp)) THEN
   RETURN;
ELSE
   EXECUTE IMMEDIATE 'TRUNCATE TABLE main';
   INSERT --+APPEND 
          INTO main
          Select * from temp;
   EXECUTE IMMEDIATE 'TRUNCATE TABLE temp';
END IF;

使用此解决方案，程序包编译时出错。

有人能给我一些提示吗？

Answer 1

你可以使用循环，没有任何变量，只需要第一次迭代，就像这样

FOR a in (select 1 from temp where rownum = 1) LOOP

   EXECUTE IMMEDIATE 'TRUNCATE TABLE main';
   INSERT --+APPEND 
          INTO main
          Select * from temp;
   EXECUTE IMMEDIATE 'TRUNCATE TABLE temp';

END LOOP;

Answer 2

只计算一行，然后测试结果是0还是1：

    $ rails c
    /Users/my_username/.rvm/gems/ruby-2.3.0/gems/actionpack-5.0.0/lib/action_controller/test_case.rb:49:in `initialize': wrong number of arguments (given 0, expected 2) (ArgumentError)
        from /Users/my_username/.rvm/gems/ruby-2.3.0/bundler/gems/draper-57a514133bc2/lib/draper/view_context/build_strategy.rb:41:in `new'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/bundler/gems/draper-57a514133bc2/lib/draper/view_context/build_strategy.rb:41:in `block in controller'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/andand-1.3.3/lib/andand.rb:60:in `me'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/bundler/gems/draper-57a514133bc2/lib/draper/view_context/build_strategy.rb:40:in `controller'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/bundler/gems/draper-57a514133bc2/lib/draper/view_context/build_strategy.rb:30:in `call'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/bundler/gems/draper-57a514133bc2/lib/draper/view_context.rb:49:in `build'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/bundler/gems/draper-57a514133bc2/lib/draper/railtie.rb:63:in `block in <class:Railtie>'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/railtie.rb:226:in `block in run_console_blocks'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/railtie.rb:247:in `each'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/railtie.rb:247:in `each_registered_block'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/railtie.rb:226:in `run_console_blocks'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/application.rb:463:in `block in run_console_blocks'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/engine/railties.rb:13:in `each'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/engine/railties.rb:13:in `each'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/application.rb:463:in `run_console_blocks'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/engine.rb:442:in `load_console'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-5.0.0/lib/rails/commands/console.rb:34:in `initialize'
        from /Users/my_username/.rvm/gems/ruby-2.3.0/gems/railties-

--clipped 441 characters to enter stack overflow question edit

Answer 3

最简单的方法是使用变量进行检查：

--- suggested edit: add condition to select 1 row at most and avoid
--  counting big table.
select count(1) into v_count from temp where rownum <=1;

IF (v_count=0) THEN
   RETURN;
ELSE
   EXECUTE IMMEDIATE 'TRUNCATE TABLE main';
   INSERT --+APPEND 
          INTO main
          Select * from temp;
   EXECUTE IMMEDIATE 'TRUNCATE TABLE temp';
END IF;

Answer 4

这里的一些答案使用了SELECT INTO方法，但我发现这些方法有点棘手。
如果例如SELECT ColumnA INTO vcColumnA FROM Temp没有任何记录，则最终会出现错误ORA-01403: no data found。
如果你有一个更大的数据库，那很难找到。

要遍历表并使用值执行某些操作，我认为游标和记录更安全。

例如：

DECLARE
    CURSOR cTemp IS 
        SELECT  ColumnA, ColumnB 
        FROM    Temp;

    rTemp   cTemp%ROWTYPE;
BEGIN
    OPEN cTemp;
    LOOP
        FETCH cTemp INTO rTemp;
        -- Exit when we read all lines in the Temp table. 
        EXIT WHEN cTemp%NOTFOUND;

        --Do something with every row. 
        --For example, print ColumnB. 
        DBMS_OUTPUT.PUT_LINE(rTemp.ColumnB);
    END LOOP;
    CLOSE cTemp;
END;
/

如果表有0行退出程序

4 个答案: