实例
SELECT City FROM Customers
UNION
SELECT City FROM Suppliers
ORDER BY City;
注释:不能用 UNION 来列出两个表中的所有城市。如果一些客户和供应商来自同一个城市,每个城市将只被列入一个列表。UNION将只选择不同的值。请使用UNION ALL选择重复值!
SQL UNION ALL 实例
以下SQL语句使用 UNION ALL 从 "Customers"和"Suppliers" 表中选择所有城市(也是重复的值):
实例
SELECT City FROM Customers
UNION ALL
SELECT City FROM Suppliers
ORDER BY City;
带有 WHERE 的 SQL UNION ALL
以下SQL语句使用UNIONALL从"Customers"和 "Suppliers" 表中选择所有德国城市(也是重复数值):
实例
SELECT City, Country FROM Customers
WHERE Country='Germany'
UNION ALL
SELECT City, Country FROM Suppliers
WHERE Country='Germany'
ORDER BY City;
SELECT City, Country FROM Customers
WHERE Country='Germany'
UNION
SELECT City, Country FROM Suppliers
WHERE Country='Germany'
ORDER BY City;
另一个UNION示例
以下SQL语句列出了所有客户和供应商:
SELECT 'Customer' As Type, ContactName, City, Country
FROM Customers
UNION
SELECT 'Supplier', ContactName, City, Country
FROM Suppliers;
还有另外两个子句(即运算符),它们类似于UNION子句: