Question

我创建了一个WITH语句，例如：

 WITH data AS(
   SELECT COUNT (*) as a, E.b as b
   FROM         table1 C
   JOIN         table2 D
   ON           D.MY_ID = C.MY_ID
   JOIN         table3 E
   ON           E.NEW_ID = C.NEW_ID
   WHERE        E.b BETWEEN 1 AND 4
   GROUP BY     E.b
   ORDER BY     E.b)

我想在这样的for循环中使用它：

BEGIN
FOR x IN 1..100 LOOP
{ WITH data AS(
       SELECT COUNT (*) as a, E.b as b
       FROM         table1 C
       JOIN         table2 D
       ON           D.MY_ID = C.MY_ID
       JOIN         table3 E
       ON           E.NEW_ID = C.NEW_ID
       WHERE        E.b BETWEEN 1 AND 4
       GROUP BY     E.b
       ORDER BY     E.b)}
END LOOP;
END;

但是oracle说我需要在这个声明中。我该怎么办？我应该使用光标吗？它看起来怎么样？

Answer 1

鉴于您只需要运行相同查询的100次，请考虑一下，无论您是否使用INTO，都必须使用WITH子句。

您可以尝试这种方式：

DECLARE
    type tab_number is table of number;
    vA tab_number;
    vB tab_number;
BEGIN
    FOR I IN 1 .. 100 LOOP
       WITH data AS(
           SELECT COUNT (*) as a, E.b as b
           FROM         table1 C
           JOIN         table2 D
           ON           D.MY_ID = C.MY_ID
           JOIN         table3 E
           ON           E.NEW_ID = C.NEW_ID
           WHERE        E.b BETWEEN 1 AND 4
           GROUP BY     E.b
           ORDER BY     E.b
       )
       SELECT A, B
       BULK COLLECT INTO vA, vB
       FROM DATA;
   END LOOP;
END;

甚至没有WITH：

DECLARE
    type tab_number is table of number;
    vA tab_number;
    vB tab_number;
BEGIN
    FOR I IN 1 .. 100 LOOP
       SELECT COUNT (*) as a, E.b as b
       BULK COLLECT INTO vA, vB
       FROM         table1 C
       JOIN         table2 D
       ON           D.MY_ID = C.MY_ID
       JOIN         table3 E
       ON           E.NEW_ID = C.NEW_ID
       WHERE        E.b BETWEEN 1 AND 4
       GROUP BY     E.b
       ORDER BY     E.b;
   END LOOP;
END;

请注意，在这些示例中，我们使用BULK COLLECT，因为您的查询可能会返回多行。如果您只需要一行，则可以删除GROUP BY子句并尝试以下内容：

DECLARE
    vA NUMBER;
BEGIN
    FOR I IN 1 .. 100 LOOP
       SELECT COUNT (*) as A
       INTO vA
       FROM         table1 C
       JOIN         table2 D
       ON           D.MY_ID = C.MY_ID
       JOIN         table3 E
       ON           E.NEW_ID = C.NEW_ID
       WHERE        E.b BETWEEN 1 AND 4;
   END LOOP;
END;

请注意，这可能不是检查查询性能的最佳方法：首次运行后，数据可能已经被缓存，因此以下运行可能会更快

Answer 2

我需要检查此声明的运行时间

您假设WITH部分独立于使用的实际查询运行，这通常是不正确的。 WITH将与使用它的部分一起编译成一个执行计划。如果你想单独检查WITH部分，那么只需取出WITH行并在其中运行`SELECT。

但是，运行整个查询或获得更好的SQL分析工具会更准确。

WITH语句中的FOR循环

2 个答案: