Question

我想从2个表中创建一个带有某种条件连接的视图（请原谅我的无知，因为我是SQL编码的新手！）。这两个表如下：

TABLE1

Store | Product | MAC Price
S001 |  123 |    15.00
S001 |  456 |    17.50 
S002 |  123 |    16.00 
S002 |  456 |    17.50 
S002 |  789 |    20.00

TABLE2：

Store | Product | SELL Price
S001 |  123 |    25.00
S001 |  456 |    27.50 
S002 |  123 |    26.00 
SNAT |  123 |    35.00 
SNAT |  456 |    40.00

我在语法上苦苦挣扎的是，TABLE2要么在商店级别（例如S001）或国家级别（例如SNAT）有价格，要么根本没有价格。

必需的观看输出：

Store | Product | MAC Price | Sell Price
S001 |  123 |    15.00 |     25.00 
S001 |  456 |    17.50 |     25.00 
S002 |  123 |    16.00 |     26.00 
S002 |  456 |    17.50 |     40.00  (no Store specifc, therefore SNAT)
S002 |  789 |    20.00 |      0.00  (no Store specifc or SNAT)

我目前的代码如下所示......我只是不知道在哪里/如何添加规则＆＃34;如果没有特定商店的价格，请使用SNAT，否则为0.00＆＃34; ...

create view SCH.Z_MAC_PRICE as
    select SCH.table1.store, SCH.table1.product, SCH.table1.mac,
           SCH.table2.sell
    from SCH.table1 left outer join
         SCH.table2
         on SCH.table1.store = SCH.table2.store and
            SCH.table1.product = SCH.table2.product

Answer 1

您需要多个left join s：

create view SCH.Z_MAC_PRICE as
    select t1.store, t1.product, t1.mac,
           coalesce(t2s.sell, t2n.sell, 0) as sell
    from SCH.table1 t1 left outer join
         SCH.table2 t2s
         on t2s.store = t1.store and
            t2s.product = t1.product left outer join
         SCH.table2 t2n
         on t2s.store = 'SNAT' and
            t2s.product = t1.product

Answer 2

我将table1加入table1 两次，一次用于商店级别，再次用于国家级别，并且仅在商店级别不存在时才显示国家级别：

CREATE VIEW z_mac_price AS
SELECT      t1.store,
            t1.product,
            t1.mac_price,
            COALESCE(t2store.sell_price, t2nat.sell_pirce, 0.00)
FROM        table1 t1
LEFT JOIN   table2 t2store ON t2store.product = t1.product AND 
                              t2store.store = t1.store
LEFT JOIN   table2 t2nat ON t2nat.product = t1.product AND 
                            t2nat.store = 'SNAT'

使用连接条件创建视图

2 个答案: