我怀疑这两种方法中哪种方法更有效,
让我们假设我有一个针对每个用户的数据库,每个用户可能有很多商店,所以我有一个表CONFIG
,其中包含诸如SHOP_CONFIG
(商店的编号)和POS_CONFIG
( POS的ID)一家商店可以拥有多个POS 。
然后我有一个带有ITEMS
的表,这些表属于属于ID_ITEMS
DESC_ITEMS
等列的商店,
每个POS
中的每个SHOP
的项目都可以相同,或者每个POS
可以具有不同的ITEMS
。所以现在我必须查看每个SHOP
/ POS
所以我的疑问是:
我应该在ID
上添加CONFIG
,然后用SHOP_ITEMS
的{{1}}作为外键,用{{1 }}作为外键?
还是我可以将ID
和CONFIG
列添加到ID_ITEMS
表中?
(表SHOP
仍用于其他目的)
答案 0 :(得分:1)
一个更长的例子,但是您可以根据您的项目进行调整。
-- Shop owner (user) OWN exists.
--
owner {OWN}
PK {OWN}
-- Owner OWN owns shop number SHP# (of that owner).
--
shop {OWN, SHP#}
PK {OWN, SHP#}
FK {OWN} REFERENCES owner {OWN}
-- Point of sale number POS#,
-- of shop number SHP#, of owner OWN exists.
--
point_of_sale {OWN, SHP#, POS#}
PK {OWN, SHP#, POS#}
FK {OWN, SHP#} REFERENCES shop {OWN, SHP#}
-- Item ITM exists.
--
item {ITM}
PK {ITM}
-- Item ITM is available in shop
-- number SHP#, of owner OWN.
--
item_shop {ITM, OWN, SHP#}
PK {ITM, OWN, SHP#}
FK1 {ITM} REFERENCES item {ITM}
FK2 {OWN, SHP#} REFERENCES shop {OWN, SHP#}
-- On DTE (date-time), item ITM was sold in
-- quantity QTY, thru point of sale number POS#,
-- of shop number SHP#, of owner OWN.
--
sales {OWN, SHP#, POS#, DTE, ITM, QTY}
PK {OWN, SHP#, POS#, DTE, ITM}
FK1 {ITM, OWN, SHP#} REFERENCES
item_shop {ITM, OWN, SHP#}
FK2 {OWN, SHP#, POS#} REFERENCES
point_of_sale {OWN, SHP#, POS#}
注意:
All attributes (columns) NOT NULL
PK = Primary Key
FK = Foreign Key
Using suffix # to save on screen space.
OK for SQL Server and Oracle, for others use _NO.
For example, rename SHP# to SHP_NO.