从另一个视图创建视图 [英] Creating View from Another View

问题描述

搜索后，我没有在网上或任何其他资源中找到任何东西，我想知道您是否可以通过联接另一个视图和一些其他表来形成一个视图?我猜类似的东西与Server_ref.part_notification_view是要加入的视图.

I haven't found anything online or in any other resource after searching, and I was wondering if you could form a View by joining another view and some other tables? Something similar to this I guess with Server_ref.part_notification_view being the view getting joined.

Create View "PART_NOTIFICATION_VIEW" ("NOTIFICATION_IX", "PART_NBR", "MFG_CD", "PART_CLASS_CD", "LEADTIME", "BILLTO_CUST_NBR", "BILL_TO_ACCT_NM", "CUST_PART_NBR", "LAST_CUST_PO", "LAST_REQ_DT", "QTY_OPEN", "YEAR_USAGE", "AVAILABLE_SALE_STANDARD_QT", "ISSUE_DATE", "EFFECTIVE_DATE", "BRIEF_DESCRIPTION", "NOTIFICATION_TYPE", "ACTUAL_DOCUMENT_LINK", "AFFECTED_PARTS_LIST_DOC_LINK", "EMAIL_LINK", "FILE_FOLDER", "RECOMMENDED_REPLACEMENT", "PCN_TYPE", "IMPACT", "MANUFACTURER_NM", "LAST_BUY_DT", "LAST_SHIP_DT", "SALES_MIN_BUY_QTY", "SALES_MIN_PKG_QTY", "PART_DESC", "BOND_QOH", "BOND_QIT", "BRANCH_QOH", "BRANCH_QIT", "BOND_QTY", "BOND_PIPELINE", "BOND_OP", "BRAND_CD", "STATUS", "COMMENTS")
AS
  SELECT
    svr.notification_ix,
    svr.part_nbr,
    svr.mfg_cd,
    svr.part_class_cd,
    svr.leadtime,
    svr.billto_cust_nbr,
    svr.bill_to_acct_nm,
    svr.cust_part_nbr,
    svr.last_cust_po,
    svr.last_req_dt,
    svr.qty_open,
    svr.year_usage,
    svr.available_sale_standard_qt,
    svr.issue_date,
    svr.effective_date,
    svr.brief_description,
    svr.notification_type,
    svr.actual_document_link,
    svr.affected_parts_list_doc_link,
    svr.email_link,
    svr.file_folder,
    svr.recommended_replacement,
    svr.pcn_type,
    svr.impact,
    svr.manufacturer_nm,
    svr.last_buy_dt,
    svr.last_ship_dt,
    svr.sales_min_buy_qty,
    svr.sales_min_pkg_qty,
    svr.part_desc,
    NVL(svr.bond_qoh, 0)                                                                    AS bond_qoh,
    NVL(svr.bond_qit, 0)                                                                    AS bond_qit,
    NVL(svr.branch_qoh, 0)                                                                  AS branch_qoh,
    NVL(svr.branch_qit, 0)                                                                  AS branch_qit,
    NVL(svr.bond_qoh, 0)      + NVL(svr.bond_qit, 0) + NVL(svr.branch_qoh, 0) + NVL(svr.branch_qit, 0) AS bond_qty,
    NVL(svr.bond_pipeline, 0) + NVL(svr.po_qt, 0)                                                 AS bond_pipeline,
    svr.bond_op,
    svr.brand_cd,
    cs.status,
    cc.comments
  FROM part_notification_view svr
  JOIN css_status cs
  ON svr.part_nbr = cs.part_nbr
  AND svr.mfg_cd = cs.mfg_cd
  AND svr.billto_cust_nbr = cs.account
  JOIN css_comment cc
  ON svr.part_nbr = cc.part_nbr
  AND svr.mfg_cd = cc.mfg_cd
  AND svr.billto_cust_nbr = cc.account;

推荐答案

您当然可以在另一个视图之上构建一个视图:

You can certainly have a view that's built on top of another view:

create table my_table (id number, name varchar2(20), address varchar2(30));

table MY_TABLE created.

create or replace view my_view_1 as
select id, name
from my_table;

view MY_VIEW_1 created.

create or replace view my_view_2 as
select mv1.id, mv1.name, mt.address
from my_view_1 mv1
join my_table mt on mt.id = mv1.id;

view MY_VIEW_2 created.

但是您不能引用基础表中的任何内容，包括不属于视图的任何字段:

But you can't reference anything in the underlying tables, including any fields that are not part of the view:

create or replace view my_view_3 as
select mv1.id, mv1.name, mv1.address
from my_view_1 mv1
join my_table mt on mt.id = mv1.id;

SQL Error: ORA-00904: "MV1"."ADDRESS": invalid identifier
00904. 00000 -  "%s: invalid identifier"

具有相同列的基础表不是问题，如果您在视图中包含的内容超过了，则无论如何都必须为其别名.

The underlying tables having the same columns isn't an issue, and if you include more than on in the view then you'd have to alias them anyway.

执行此操作有时可能会遇到性能问题，如果您针对相同的基表创建新视图，并对其进行扩展以包含所需的额外数据，则可能会更快，更可靠(尽管可能更难维护).

You can sometimes get performance issues doing this, and it might be faster and more reliable - though possibly harder to maintain - if you create your new view against the same base tables, and expand it to include the extra data you want.

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