一.group by statement（语句）
1.group by通常和聚合函数（count,max,min,sum,avg）一起使用，显示一列或多列
SELECT column_name(s) FROM table_name WHERE condition GROUP BY column_name(s) ORDER BY column_name(s);
eg.显示每一个国家的客户数量
SELECT COUNT(CustomerID), Country FROM Customers GROUP BY Country;
eg.显示每一个国家的客户数量，并且按照由高到低排列
SELECT COUNT(CustomerID), Country FROM Customers GROUP BY Country ORDER BY COUNT(CustomerID) DESC;
eg.显示每一个投递员的订单数量
SELECT Shippers.ShipperName, COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders LEFT JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID GROUP BY ShipperName;
二.having
1.
三.select into statement（语句）
1.把表格中的所有数据复制到一个新的表格中
SELECT *
INTO newtable [ IN externaldb ]FROM table1;
eg.创建数据备份
SELECT * INTO CustomersBackup2013 FROM Customers;
eg.把一个表格复制到另一个数据库里
SELECT * INTO CustomersBackup2013 IN 'Backup.mdb' FROM Customers;
2.把表格中的部分列复制到一个新的表格中
SELECT column_name(s) INTO newtable [IN externaldb] FROM table1;
注：新复制来的表格中会默认用之前的列名称和类型，也可以用as子句来更换名称
eg.把一个表格中的部分列复制到另一个新的表格里
SELECT CustomerName, ContactName INTO CustomersBackup2013 FROM Customers;
3.select...into...where
eg.把customers表格中的country列中的Germany的数据复制到另一个新的表格里
SELECT * INTO CustomersBackup2013 FROM Customers WHERE Country='Germany';
4.把多个表格中的数据复制到另一个新的表格里
SELECT Customers.CustomerName, Orders.OrderID INTO CustomersOrderBackup2013 FROM Customers LEFT JOIN Orders ON Customers.CustomerID=Orders.CustomerID;
5.创建一个新的空的表格
SELECT * INTO newtable FROM table1 WHERE 1=0;
四.insert into select statement（语句）
1.把一个表格中的所有数据全部复制进另一个已经存在的表格里
INSERT INTO table2 SELECT * FROM table1;
2.复制一个表格中的部分列到另一个已经存在的表格里
INSERT INTO table2 (column_name(s)) SELECT column_name(s) FROM table1;
eg.把suppliers表格中的suppliername列和country列，复制进customers表格中
INSERT INTO Customers (CustomerName, Country) SELECT SupplierName, Country FROM Suppliers;
eg.把suppliers表格中的suppliername列和country列，且country列中是germany的数据，复制进customers表格中
INSERT INTO Customers (CustomerName, Country) SELECT SupplierName, Country FROM Suppliers WHERE Country='Germany';
五.comments
1.
