需要帮助 MS Access Select 请求使用 2 个表

Question

For a "products reservation system", I have 2 tables:

• "RD", for global reservations data (fieds: ID, CustomerID, Date, ...)
• "RP", for reserved products data per reservation (fields: ID, RD_ID, ProductID, Status, ...). RD_ID fits with the ID in RD table (field for joining). Status field can have these values: O, C, S.

I need to extract (with 2 Select instructions) the list of reservations and the number of reservations for which all products have status 'O'.

Data example for RP:

ID | RD_ID | ProdID | Status
----------------------------
1  | 1     | 100    | O
2  | 1     | 101    | O
3  | 1     | 102    | O
4  | 2     | 105    | O
5  | 2     | 100    | S
6  | 3     | 101    | C
7  | 3     | 102    | O

In this example, Select statement should return only RD_ID 1

For the number of ID, the following request does not work because it also includes reservations with products having different status:

SELECT COUNT(rd.ID) FROM rd INNER JOIN rp ON rp.RD_ID = rd.ID WHERE rp.Status = 'O';

Could you help me for the right Select statement?

Thank you.

Answer 1

SELECT rd.ID, COUNT(rd.ID) CountOfRD, status FROM rd INNER JOIN rp ON rp.RD_ID GROUP BY rd.ID, status

Answer 2

Use not exists as follows:

Select t.* from your_table t
Where t.status = 'O'
  And not exists (select 1 from your_table tt
                   Where t.rd_id = tt.rd_id
                     And t.status != tt.status)

You can also use group by and having as follows:

Select rd_id
  From your_table t
Group by rd_id
Having sum(case when status <> 'O' then 1 end) > 0