SQL CX，這是什麼意思

Question

我有SQL語法像這樣

WITH cx (Policy_Number,Claim_Incurred) 

    AS (

    SELECT PolicyNo 

     ,SUM(ReservedAmt + PaidAmt - SalvageAmt + ReservedExp + PaidExp - SalvageExp) 

    FROM eInsurance.dbo.Claim 

    GROUP BY PolicyNo 

) 

或像這樣

REFERENCE.dbo.FXRate fx 
    JOIN eInsurance.dbo.PolicyM pm 
     ON fx.currency = pm.PRCurrency 
    LEFT JOIN cx 
     ON pm.PolicyNo = cx.Policy_Number 
    JOIN eInsurance.dbo.Account acc 
     ON pm.AccCode = acc.AccCode 
    JOIN eInsurance.dbo.AccTypeList atl 
     ON acc.AccType = atl.TypeCode 

那麼，是什麼CX在其語法意味着..？

Answer 1

cx被稱爲公用表表達式，通常稱爲CTE。

您可以將其視爲數據的臨時視圖，僅針對單個查詢定義。您可以將cx替換爲with子句中的定義。