DB2 存储过程中执行动态SQL

Posted 2020-12-05

样本代码：

DROP PROCEDURE QUOTATION.COPY_SAMPLE;
CREATE PROCEDURE QUOTATION.COPY_SAMPLE (
    IN tableNameFrom VARCHAR(30)
    , IN tableNameTo VARCHAR(30)
    , INOUT copyResult INTEGER)

BEGIN
    DECLARE SQLCODE INTEGER DEFAULT 0;

    SET copyResult = 0;

    -- Proecss 1
    BEGIN
        DECLARE fromSql VARCHAR(32672);
        DECLARE toSql VARCHAR(32672);
        DECLARE templateParserId INTEGER;
        DECLARE uuid VARCHAR(36);
        DECLARE stmt STATEMENT;
        DECLARE curs CURSOR FOR stmt;

        SET fromSql = ‘SELECT TEMPLATE_PARSER_ID, UUID FROM QUOTATION.‘ || tableNameFrom;
        PREPARE stmt FROM fromSql;
        OPEN curs;
        CURSORLOOP:
            LOOP
                FETCH curs INTO templateParserId, uuid;
                -- Do nothing if no data or processed all datas.
                IF SQLCODE = 100 THEN LEAVE CURSORLOOP;
                END IF;

                SET toSql = ‘INSERT INTO QUOTATION.‘ || tableNameTo || ‘ (TEMPLATE_PARSER_ID, UUID) VALUES (‘ || templateParserId || ‘,‘‘‘ || uuid || ‘‘‘)‘;
                PREPARE s FROM toSql;
                EXECUTE s;
            END LOOP;
        CLOSE curs;
    END;

    -- Proecss 2
    BEGIN
        -- ......
    END;

    SET copyResult = 1;
END;

注意点：
1、SQLCODE必须要定义，且必须定义在最外层的BEGIN的下面。
2、必须要判断SQLCODE是否等于100，等于100时退出CURSORLOOP，否则会死循环。
3、“OPEN curs”之后不要忘记“CURSORLOOP:”。
4、在DB2中动态SQL中如果包含SELECT或者VALUES是不能直接执行的(如：以上代码中的：PREPARE s FROM toSql;EXECUTE s;)，必须使用“OPEN curs”的写法。