如何在SQL Server 2019中将两个SQL查询结果合并为单个结果集

你可以直接用条件聚合实现需求，仅需一次查询即可得到目标结果，性能比分别查询再关联更优，适配SQL Server 2019 Express版本：

SELECT 
    s.SaleDate,
    SUM(s.SaleAmt) AS [Total Sales from All],
    SUM(CASE WHEN EXISTS (SELECT 1 FROM Customers c WHERE c.CustomerID = s.CustomerID) 
        THEN s.SaleAmt ELSE 0 END) AS [Total Sales from Customers]
FROM Sales s
GROUP BY s.SaleDate
ORDER BY s.SaleDate

如果你需要保留原有两个查询的逻辑进行合并，可以通过INNER JOIN关联两个子查询的结果：

SELECT 
    t1.SaleDate,
    t1.[Total Sales from All],
    t2.[Total Sales from Customers]
FROM 
(
    SELECT sales.saledate, SUM(sales.saleamt) AS [Total Sales from All] 
    FROM Sales 
    GROUP BY sales.saledate
) t1
INNER JOIN
(
    SELECT sales.saledate, SUM(sales.saleamt) AS [Total Sales from Customers]
    FROM Sales 
    WHERE sales.customerid IN (SELECT customerid FROM customers) 
    GROUP BY sales.saledate
) t2 ON t1.SaleDate = t2.SaleDate
ORDER BY t1.SaleDate

两种写法都可以得到你预期的结果：

内容的提问来源于stack exchange，提问作者TurboSonic