SQL CX，这是什么意思

Question

我有SQL语法像这样

WITH cx (Policy_Number,Claim_Incurred) 

    AS (

    SELECT PolicyNo 

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

    FROM eInsurance.dbo.Claim 

    GROUP BY PolicyNo 

) 

或像这样

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 

那么，是什么CX在其语法意味着..？

Answer 1

cx被称为公用表表达式，通常称为CTE。

您可以将其视为数据的临时视图，仅针对单个查询定义。您可以将cx替换为with子句中的定义。