DB2 存储过程:动态构建游标的选择语句

Question

我对存储过程相当陌生。我天真地认为我可以建立一个如下选择语句。我不能，你们中的一些人会对我想出的东西咧嘴一笑。

一个人如何做我想做的事情？

提前谢谢。

CREATE PROCEDURE GET_CUSTOMER_FOR_BORROWER_LETTER (

    IN APPLICATION_ID INTEGER,
    IN GET_GUARANTOR INTEGER,
    IN GET_PREFERRED_CONTACT INTEGER
    )
DYNAMIC RESULT SETS 1
READS SQL DATA
P1:BEGIN
    DECLARE selectStmt VARCHAR(800);
    DECLARE selectStmtPreferred VARCHAR(400);
    DECLARE selectStmtApplicants VARCHAR(400);
    DECLARE selectStmtGuarantor VARCHAR(400);

    DECLARE cursor1 CURSOR WITH RETURN FOR
    selectStmt -- will define this later, conditionally (babe in the woods :) )
    OPEN cursor1;

    set selectStmtPreferred = 'select "preferred applicant" as recipient_type, app.APPLICATION_ID, cust.KEY from application app, customer cust, application_detail appd where app.application_id = 407634 and app.APPLICATION_ID = appd.APPLICATION_ID  and appd.PREFERRED_CONTACT_ID = cust.KEY';
    set selectStmtApplicants = 'select "applicant" as recipient_type, app.APPLICATION_ID, cust.KEY from application app, applicant applc, customer cust where app.application_id = 407634 and applc.APPLICATION_ID = app.APPLICATION_ID and applc.CUST_ID = cust.CUST_ID';
    set selectStmtGuarantor = ' union select "guarantor" as recipient_type ,app.APPLICATION_ID, cust.KEY from application app, application_guarantor appg, customer cust where app.application_id = 407634 and appg.APPLICATION_ID = app.APPLICATION_ID and appg.CUST_ID = cust.CUST_ID';
    IF GET_PREFERRED_CONTACT = 1 THEN
        IF GET_GUARANTOR = 1 THEN 
            SET selectStmt = concat (selectStmtPreferred,selectStmtGuarantor);
        ELSE 
            SET selectStmt = selectStmtPreferred;
        END IF;
    ELSE 
        IF GET_GUARANTOR = 1 THEN 
            SET selectStmt = concat (selectStmtApplicants,selectStmtGuarantor);
        ELSE 
            SET selectStmt = selectStmtApplicants;
        END IF;
    END IF;
selectStmt = concat (selectStmtPreferred,";");

END P1@

Answer 1

下次需要构建一些动态 SQL 语句时，请尝试此操作。

DECLARE SELECT_STATEMENT VARCHAR(8000);
DECLARE cursor1 CURSOR WITH RETURN FOR SQL_STATEMENT;
...build dynamic sql here...
PREPARE SQL_STATEMENT FROM SELECT_STATEMENT;
OPEN cursor1;

需要明确的是，SQL_STATEMENT是您想要的任何名称。 只需确保它在 CURSOR 声明和 PREPARE 语句中是相同的。

Answer 2

我解决了这个问题。它很丑陋，但它已经解决了。

P1:BEGIN
    DECLARE preferredWithGuarantor CURSOR WITH RETURN FOR
            select 'preferred applicant' as recipient_type, app.APPLICATION_ID, cust.KEY from application app, customer cust, application_detail appd where app.application_id = 407634 and app.APPLICATION_ID = appd.APPLICATION_ID  and appd.PREFERRED_CONTACT_ID = cust.KEY union select 'guarantor' as recipient_type ,app.APPLICATION_ID, cust.KEY from application app, application_guarantor appg, customer cust where app.application_id = 407634 and appg.APPLICATION_ID = app.APPLICATION_ID and appg.CUST_ID = cust.CUST_ID;
    DECLARE preferred CURSOR WITH RETURN FOR
            select 'preferred applicant' as recipient_type, app.APPLICATION_ID, cust.KEY from application app, customer cust, application_detail appd where app.application_id = 407634 and app.APPLICATION_ID = appd.APPLICATION_ID  and appd.PREFERRED_CONTACT_ID = cust.KEY;
    DECLARE applicantWithGuarantor CURSOR WITH RETURN FOR
            select 'applicant' as recipient_type, app.APPLICATION_ID, cust.KEY from application app, applicant applc, customer cust where app.application_id = 407634 and applc.APPLICATION_ID = app.APPLICATION_ID and applc.CUST_ID = cust.CUST_ID union select 'guarantor' as recipient_type ,app.APPLICATION_ID, cust.KEY from application app, application_guarantor appg, customer cust where app.application_id = 407634 and appg.APPLICATION_ID = app.APPLICATION_ID and appg.CUST_ID = cust.CUST_ID;
    DECLARE applicant CURSOR WITH RETURN FOR
            select 'applicant' as recipient_type, app.APPLICATION_ID, cust.KEY from application app, applicant applc, customer cust where app.application_id = 407634 and applc.APPLICATION_ID = app.APPLICATION_ID and applc.CUST_ID = cust.CUST_ID;

    IF GET_PREFERRED_CONTACT = 1 THEN
        IF GET_GUARANTOR = 1 THEN 
            open preferredWithGuarantor;
        ELSE 
            open preferred;
        END IF;
    ELSE 
        IF GET_GUARANTOR = 1 THEN 
            open applicantWithGuarantor;
        ELSE
            open applicant;
        END IF;
    END IF;
END P1@