假設我有一個表，它包含個人和公司的一些數據，並且如果沒有爲個人或公司找到數據，我想檢索默認值，例如，假設我有一個表sql如果未找到結果，請選擇默認行

CustomerAccountId CustomerAccountType  DueDays  IsAdjustable isDefaultForIndividual isDefaultForCompany  
1     Individual    10   true   false     false 
2     Company     20   false   false     false 
null    null     5   false   true     false 
null    null     30   true   false     true

我想創建一個函數有兩個參數IndividualCustomerAccountId和CompanyCustomerAccountId如果IndividualCustomerAccountId在表中找到檢索它，如果沒有找到檢索個人的默認值，它是在這種情況下, the same for companies, if the CompanyCustomerAccountId的third rowis found retrieve it, if not get the default value for the companies which is第四行在這種情況下。

假設我們創建了接受IndividualCustomerAccountId作爲第一個參數和CompanyCustomerAccountId作爲第二個參數funtion

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MyFunc(1 , 2)應該返回first and second rows

MyFunc(1 , 50)應該返回first and fourth rows，因爲沒有一家公司與CustomerAccountId50在表中找到所以檢索c的默認值ompanies因爲客戶的賬戶ID 100沒有任何人士被發現這是fourth row

MyFunc(100 , 2)應該返回second and third rows所以我們得到了個人的默認值是third row，我們有customerAccountId 2一個公司，所以我們根本就retrive它從桌子上。

我想創建無論是LINQ查詢或SQL函數來實現這些結果

來源

2017-04-09 Nader Hisham

[這可能有助於]（http://stackoverflow.com/a/285823/5707687） –

我將假設正常化您的數據不是一種選擇？更好的設計會更容易查詢。 – Crowcoder

@Crowcoder你是對的，但不幸的是，我們現在不能改變DB設計 –

你可以嘗試SQL函數

CREATE TABLE Customer 
(
    CustomerAccountId int, 
    CustomerAccountType varchar(20), 
    DueDays int, 
    IsAdjustable bit, 
    isDefaultForIndividual bit, 
    isDefaultForCompany bit 
) 

INSERT INTO Customer VALUES 
(1, 'Individual', 10, 1,0,0), 
(2, 'Company', 20, 0,0,0), 
(null, null, 5, 0,1,0), 
(null, null, 30, 1,0,1) 

GO 

CREATE FUNCTION MyFunc 
(
@IndividualCustomerAccountId int, 
@CompanyCustomerAccountId int 
) 
RETURNs @result TABLE 
(
    CustomerAccountId int, 
    CustomerAccountType varchar(20), 
    DueDays int, 
    IsAdjustable bit, 
    isDefaultForIndividual bit, 
    isDefaultForCompany bit 
) 
BEGIN 

    INSERT INTO @result 
    SELECT CustomerAccountId , CustomerAccountType, DueDays, IsAdjustable, isDefaultForIndividual,isDefaultForCompany 
    FROM Customer c 
    WHERE (CustomerAccountId = @IndividualCustomerAccountId AND CustomerAccountType = 'Individual') 
      OR (CustomerAccountId = @CompanyCustomerAccountId AND CustomerAccountType = 'Company') 

    IF(NOT EXISTS (SELECT 1 FROM Customer c 
        WHERE CustomerAccountId = @IndividualCustomerAccountId AND CustomerAccountType = 'Individual')) 
    BEGIN 
     INSERT INTO @result 
     SELECT CustomerAccountId , CustomerAccountType, DueDays, IsAdjustable, isDefaultForIndividual,isDefaultForCompany 
     FROM Customer c 
     WHERE CustomerAccountId IS NULL AND isDefaultForIndividual = 1 
    END 

    IF(NOT EXISTS (SELECT 1 FROM Customer c 
        WHERE CustomerAccountId = @CompanyCustomerAccountId AND CustomerAccountType = 'Company')) 
    BEGIN 
     INSERT INTO @result 
     SELECT CustomerAccountId , CustomerAccountType, DueDays, IsAdjustable, isDefaultForIndividual,isDefaultForCompany 
     FROM Customer c 
     WHERE CustomerAccountId IS NULL AND isDefaultForCompany = 1 
    END 

    RETURN; 
END 

GO 


SELECT * from dbo.MyFunc(1,2) 
SELECT * from dbo.MyFunc(1,50) 
SELECT * from dbo.MyFunc(100,2) 
SELECT * from dbo.MyFunc(100,50) 
--DROP TABLE Customer

演示鏈接：Rextester

來源

2017-04-09 13:42:16 TriV

基本上，你可以運行若您在使用查詢存在，看看是否有將是任何數據。如果是這樣，請繼續並運行您的查詢。如果不是，請執行選擇默認行。

If Exists (your query) 

     (your query) 

Else 

     SELECT 'query for default row'

我希望它清楚你的問題。
快樂Coding.Thanks

來源

2017-04-09 13:12:00

sql如果未找到結果，請選擇默認行

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