从 PL/SQL 函数返回大字符串

Question

这是一个 PL/SQL 函数，我遇到的问题是，当它返回一个大字符串时，它会生成以下消息：

选择 TODAS_NOTIFIACIONES_ACTIVAS('21/10/2023', 0, 10) 作为结果 FROM DUAL 命令行错误：1 列：8 错误报告 - SQL 错误： ORA-01489: 字符串连接的结果太长 ORA-06512: at “NOTIFICACIONES_PKG”，第 95 行

00000 - “字符串连接的结果太长” *原因：字符串拼接结果超过最大长度。 *操作：确保结果小于最大尺寸

这是功能代码：

FUNCTION TODAS_NOTIFICACIONES_ACTIVAS(fecha_val IN VARCHAR2, start_position IN NUMBER, end_position IN NUMBER)
RETURN CLOB
AS
    l_result1 CLOB;
    l_result2 CLOB;
    l_result3 CLOB;

    l_count NUMBER;
BEGIN

    SELECT COUNT(*) INTO l_count
    FROM NOTIFICATIONS
    WHERE TO_DATE(fecha_val, 'DD/MM/YYYY') >= NOTIFICATION_DATE_FROM
      AND TO_DATE(fecha_val, 'DD/MM/YYYY') <= NOTIFICATION_DATE_TO;

    l_result1 := '{ "count": ' || TO_CHAR(l_count) || ', "data": ';

    SELECT '[' ||
           LISTAGG(
               '{ "ID": "' || ID || '", "RECIPIENTS": "' || RECIPIENTS || '", "AGE_FROM": "' || AGE_FROM || '", "AGE_TO": "' || AGE_TO || '", "DEPARTMENT": "' || DEPARTMENT_ID || '", "LOCALITY": "' || LOCALITY_ID || '", "MESSAGE_TITLE": "' || MESSAGE_TITLE || '", "MESSAGE_BODY": "' || MESSAGE_BODY || '", "MULTIMEDIA_ID": "' || MULTIMEDIA_ID || '", "NOTIFICATION_DATE_FROM": "' || TO_CHAR(NOTIFICATION_DATE_FROM, 'DD/MM/YYYY HH24:MI:SS') || '", "NOTIFICATION_DATE_TO": "' || TO_CHAR(NOTIFICATION_DATE_TO, 'DD/MM/YYYY HH24:MI:SS') || '", "SEND_BY_EMAIL": "' || SEND_BY_EMAIL || '", "CREATED_AT": "' || TO_CHAR(CREATED_AT, 'DD/MM/YYYY HH24:MI:SS') || '", "DELETED_AT": "' || TO_CHAR(DELETED_AT, 'DD/MM/YYYY HH24:MI:SS') || '"}',
               ', '
           ) WITHIN GROUP (ORDER BY CREATED_AT DESC) ||
           ']' INTO l_result2
    FROM (
        SELECT 
            ID, RECIPIENTS, AGE_FROM, AGE_TO, DEPARTMENT_ID, LOCALITY_ID, 
            MESSAGE_TITLE, MESSAGE_BODY, MULTIMEDIA_ID, 
            NOTIFICATION_DATE_FROM, NOTIFICATION_DATE_TO, SEND_BY_EMAIL, 
            CREATED_AT, DELETED_AT,
            ROW_NUMBER() OVER (ORDER BY CREATED_AT DESC) AS rn
        FROM NOTIFICATIONS
        WHERE TO_DATE(fecha_val, 'DD/MM/YYYY') >= NOTIFICATION_DATE_FROM
          AND TO_DATE(fecha_val, 'DD/MM/YYYY') <= NOTIFICATION_DATE_TO
    )
    WHERE rn BETWEEN start_position AND end_position;

    
    l_result3 := l_result1 ||l_result2 || '}';

    RETURN l_result3;
END;

尝试修复它，我尝试了使用 start_position 和 end_position 的“分页”方法，但我不知道哪一列号不会返回该错误。例如，对于 10 行，它工作正常，直到出现错误新的通知消息。还有其他方法可以修复它吗？退货前有什么需要牢记的注意事项或初步检查吗？

Answer 1

如果您想在 Oracle 中创建 JSON，那么从 Oracle 12 开始，请使用 JSON 函数，并且不要尝试手工制作 JSON 字符串（对于初学者来说，当字符串太长时，它会失败，但您也不会处理任何转义字符可能会出现在字符串中）。

类似这样的：

CREATE FUNCTION TODAS_NOTIFICACIONES_ACTIVAS(
  fecha_val IN VARCHAR2,
  start_position IN NUMBER,
  end_position IN NUMBER
) RETURN CLOB
AS
    l_json CLOB;
BEGIN
    SELECT JSON_OBJECT(
             KEY 'count' VALUE COUNT(*),
             KEY 'data' VALUE JSON_ARRAYAGG(
               JSON_OBJECT(
                 KEY 'ID' VALUE id,
                 KEY 'RECIPIENTS' VALUE recipients,
                 KEY 'AGE_FROM' VALUE age_from,
                 KEY 'AGE_TO' VALUE age_to,
                 KEY 'DEPARTMENT' VALUE department_id,
                 KEY 'LOCALITY' VALUE locality_id,
                 KEY 'MESSAGE_TITLE' VALUE message_title,
                 KEY 'MESSAGE_BODY' VALUE message_body,
                 KEY 'MULTIMEDIA_ID' VALUE multimedia_id,
                 KEY 'NOTIFICATION_DATE_FROM' VALUE TO_CHAR(notification_date_from, 'DD/MM/YYYY HH24:MI:SS'),
                 KEY 'NOTIFICATION_DATE_TO' VALUE TO_CHAR(notification_date_to, 'DD/MM/YYYY HH24:MI:SS'),
                 KEY 'SEND_BY_EMAIL' VALUE send_by_email,
                 KEY 'CREATED_AT' VALUE TO_CHAR(created_at, 'DD/MM/YYYY HH24:MI:SS'),
                 KEY 'DELETED_AT' VALUE TO_CHAR(deleted_at, 'DD/MM/YYYY HH24:MI:SS')
                 RETURNING CLOB
               )
               RETURNING CLOB
             )
             RETURNING CLOB
           )
    INTO   l_json
    FROM   NOTIFICATIONS
    WHERE  TO_DATE(fecha_val, 'DD/MM/YYYY') >= NOTIFICATION_DATE_FROM
    AND    TO_DATE(fecha_val, 'DD/MM/YYYY') <= NOTIFICATION_DATE_TO;

    RETURN l_json;
END;
/

（如果需要，请重新应用分页。）