在 SQL 服务器中使用内连接时如何排除不相关的数据？

Question

I have 2 tables in hand. Table_A contains the Sales Date, fruit type, quantity sold and total price. Table_B contains the Unit Price of different type of fruit at different time period.

Table_A:

Sales_Date    Fruit     Quantity  Total_Price
20200515      Apple        2          4 
20200601      Apple        4          10
20200601      Banana       4          7.2
20200606      Orange       6          7.8

Table B:

Fruit      Valid_Price_From     Valid_Price_To     Unit_Price 
Apple         20200301            20200531          2.0
Banana        20200301            20200531          1.5
Orange        20200301            20200531          1.0
Apple         20200601            20200831          2.5
Banana        20200601            20200831          1.8
Orange        20200601            20200831          1.3

I'm required to form a table C combining sales related info with Unit Price which is valid within that period with this format.

Table C:

Sales_Date      Fruit      Quantity     Unit_Price    Total_Price
20200515        Apple         2             2             4 
20200601        Apple         4            2.5            10
20200601        Banana        4            1.8            7.2
20200606        Orange        6            1.3            7.8

The first query that I used was

select A.Sales_Date, A.Fruit, A.Quantity, B.Unit_Price, A.Total Price
from table_A A 
inner join
table_B B on A.Fruit=B.Fruit

But I got an error when joining these 2 tables.

I guess it is caused by there are 2 types of Unit Price (valid in different periods) for each type of fruit. Then, I tried to compare the Sales_Date with the Valid_Price_From and Valid_Price_To

The second query that I used was:

select A.Sales_Date, A.Fruit, A.Quantity, B.Unit_Price, A.Total Price
from table_A A 
inner join
table_B B on A.Fruit=B.Fruit
where A.Sales_Date > B.Valid_Price_From and A.Sales_Date < B.Valid_Price_To

But it didn't work properly as well.

May I know how should I construct my inner join query to get the desired output as shown in Table C?

Answer 1

Your date comparisons are not correct in your query:

select A.Sales_Date, A.Fruit, A.Quantity, B.Unit_Price, A.Total_Price
from table_A A inner join
     table_B B
     on A.Fruit = B.Fruit and
        A.Sales_Date >= B.Valid_Price_From and 
        A.Sales_Date <= B.Valid_Price_To;

In other words, you are not including the beginning and end dates, but your data model suggests that you do want to include them.

If you are concerned about filtering out rows with no matches -- well, you might need to fix your data. But you can keep then using left join instead of inner join .