使用If else或case方法合并多个相关的火鸟选择过程。

Question

如何使用这个REFERENCE变量通过if else、case或其他方法合并这两个火鸟选择过程。如果REFERENCE = 1，那么程序1将显示，如果REFERENCE = 2，那么程序2将显示。我试图使用1个带条件的选择过程，而不是2个过程。

CREATE PROCEDURE PRINT_NON_REF1(
      M VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      Y VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      REFERENCE VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1)
    RETURNS(
      AP_PSTIONLVL_NON VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      AP_POSTION_NON VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      RANKING_MONTH VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      RANKING_YEAR VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1)
    AS
    BEGIN
      FOR
        SELECT
          '',
          '',
          RANKING_MONTH,
          RANKING_YEAR

        FROM APPLICANT
        WHERE RANKING_MONTH = :M AND RANKING_YEAR = :Y

        GROUP BY
        RANKING_MONTH,
        RANKING_YEAR

        INTO
          :AP_PSTIONLVL_NON,
          :AP_POSTION_NON,
          :RANKING_MONTH,
          :RANKING_YEAR
      DO
        BEGIN
          SUSPEND;
        END

    END;

而且

CREATE PROCEDURE PRINT_NON_REF2(
      M VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      Y VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      REFERENCE VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1)
    RETURNS(
      AP_PSTIONLVL_NON VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      AP_POSTION_NON VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      RANKING_MONTH VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1,
      RANKING_YEAR VARCHAR(50) CHARACTER SET ISO8859_1 COLLATE ISO8859_1)
    AS
    BEGIN
      FOR
        SELECT
          AP_PSTIONLVL_NON,
          AP_POSTION_NON,
          RANKING_MONTH,
          RANKING_YEAR

        FROM APPLICANT
        WHERE RANKING_MONTH = :M AND RANKING_YEAR = :Y

        GROUP BY
        AP_PSTIONLVL_NON,
        AP_POSTION_NON,
        RANKING_MONTH,
        RANKING_YEAR

        INTO
          :AP_PSTIONLVL_NON,
          :AP_POSTION_NON,
          :RANKING_MONTH,
          :RANKING_YEAR
      DO
        BEGIN
          SUSPEND;
        END

    END;

Answer 1

你可以试试这样的构造。

WITH
  Q_2 as (
      SELECT
        AP_PSTIONLVL_NON,
        AP_POSTION_NON,
        RANKING_MONTH,
        RANKING_YEAR
      FROM APPLICANT
      WHERE RANKING_MONTH = :M
        AND RANKING_YEAR = :Y
      GROUP BY
        AP_PSTIONLVL_NON,
        AP_POSTION_NON,
        RANKING_MONTH,
        RANKING_YEAR
  ), 
  Q_1 as (
     SELECT
       '',
       '',
       RANKING_MONTH,
       RANKING_YEAR
     FROM APPLICANT
     WHERE RANKING_MONTH = :M 
       AND RANKING_YEAR = :Y
     GROUP BY
       RANKING_MONTH,
       RANKING_YEAR
 )

SELECT * FROM Q_2 WHERE :REFERENCE=2
   UNION ALL
SELECT * FROM Q_1 WHERE :REFERENCE=1

需要注意的是：

• 制作一个只包含一个存储过程的存储过程。SELECT 在FirebirdInterbase中是个坏主意。它将在加入时禁用SQL优化器工作，并且不会增加任何价值。Firebird不是MS SQL。
• 中先设置第二个查询。union的链，因为它是第一个查询的地方。UNION 从列名和数据类型。会 Q_1 先走--两个匿名列将是一个问题。
• 有些数据库访问库可能会出现一个查询中几个参数名称相同的问题。你可能需要重新命名 :M 变成 :M_1 和 :M_2，等等。也可能不是，测试一下你的库。
• 你的特定编程语言库可能有不同的SQL参数语法，而不是 :name 以上使用的。特别是，Firebird本身在SQL层面只支持未命名的参数。检查你的库文档。你也可以在阅读代码示例时得到启示，在 https:/bobby-tables.com。
• 阅读有关文件 UNION 和CTE(通用表格表达式)的情况。https:/firebirdsql.orgfiledocumentationreference_manualsfblangref25-enhtmlfblangref25-dml-select.html。