連接兩個表 - 在2個獨立的條件

Question

過濾我有兩個表： 表1

Customer|Seller Currency|Invoice #|Invoice Currency 

ABC  |USD   |123  |MXP 

我有一個第二表，其中我存儲我的客戶

表2的銀行帳戶

Customer | Bank Account | Currency 
ABC  | BANK1  | MXP 
ABC  | BANK2  | INP 
ABC  | BANK3  | USD 

我想加入這兩個表，所以當我creati NG的儀表板，我可以顯示以下內容：

如果客戶ABC在發票幣種的銀行帳戶，然後顯示，銀行賬戶（在這種情況下，結果將是BANK1）

如果客戶沒有銀行賬戶發票的貨幣，然後顯示在客戶的貨幣的銀行賬戶（在這種情況下，將區塊3

別的不顯示「沒有有效的銀行帳戶」

當我「M加入我的表是將多個記錄....我怎麼能做到這一點？

Answer 1

讓我們把你的兩個表customer_invoices和customer_accounts。

您可以使用下面的查詢與 LEFT JOIN S（所以，如果沒有銀行賬戶的存在，我們仍然保持留下數據，以及一個GROUP BY（萬一有人在給定的貨幣不止一個銀行賬戶，我們不顯示全部）：

SELECT 
    customer_invoices.customer, 
    customer_invoices.seller_currency, 
    customer_invoices.invoice_number, 
    customer_invoices.invoice_currency, 
    coalesce(min(account_invoice_currency.bank_account), 
       min(account_seller_currency.bank_account), 
       'no valid bank account') AS chosen_bank_account 
FROM 
    customer_invoices 
    LEFT JOIN customer_accounts AS account_seller_currency 
     ON  account_seller_currency.customer = customer_invoices.customer 
      AND account_seller_currency.currency = customer_invoices.seller_currency 
    LEFT JOIN customer_accounts AS account_invoice_currency 
     ON  account_invoice_currency.customer = customer_invoices.customer 
      AND account_invoice_currency.currency = customer_invoices.invoice_currency 
GROUP BY 
    customer_invoices.customer, customer_invoices.seller_currency, 
    customer_invoices.invoice_number, customer_invoices.invoice_currency ; 

您將獲得：

 
customer | seller_currency | invoice_number | invoice_currency | chosen_bank_account 
:------- | :-------------- | -------------: | :--------------- | :------------------ 
ABC  | USD    |   123 | MXP    | BANK1    

您可以在dbfiddle檢查整個安裝here個

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參考文獻：

• COALESCE()
• LEFT JOIN