java - 大表映射到另一个表

Question

让我们看一下这个场景: 我有相当多的大表，大约有 500 行和 5 列。 现在根据 col1 和 col2 的值，我想更新不同表中 col3 的值。

例如。列1 列2 列3

       a   b   ab
       c   d   cd
       x   y   xy
       .   .   ..
       .   .   ..
       .   .   ..

我想获取 col3 的值(基于 col1 和 col2 的值)并将其存储到某个不同的表中。

对于 ex2。列1 列2 列3

         good    fine       nice 

       ample  sufficient  adequate
         .            .            .
         .            .            .

请您指导我是否有 Java 或 Oracle 中的任何概念，以便我可以实现我的目的。

Answer 1

就这样？

/* CREATE TABLE exampl1 AS (SELECT 'a' AS a,'b' AS b,'c' AS c FROM dual UNION
                        SELECT 'k' AS a,'l' AS b,'n' AS c FROM dual UNION
                        SELECT 'x' AS a,'y' AS b,'z' AS c FROM dual);


CREATE TABLE exampl2 AS (SELECT 'a' AS a,'b' AS b,'_' AS c FROM dual UNION
                        SELECT 'k' AS a,'l' AS b,'_' AS c FROM dual UNION
                        SELECT 'x' AS a,'y' AS b,'_' AS c FROM dual); */                       

BEGIN
  FOR c1 IN (SELECT *
               FROM exampl1)
  LOOP
    UPDATE exampl2 t2
       SET t2.c = c1.c
     WHERE t2.a = c1.a
       AND t2.b = c1.b;
  END LOOP;
END;