1.从表中选择积分大于3000分的顾客
    SELECT *
    FROM Customers
    WHERE points > 3000

    2.从表中选择位置属于VA的顾客
    SELECT *
    FROM Customers
    WHERE state = ‘VA’

    3.从表中选择位置不属于VA的顾客
    第一种写法 （not equal运算符)
    SELECT
    FROM Customers
    WHERE state != ‘VA’
    第二种写法（<>运算符）
    SELECT
    FROM Customers
    WHERE state <> ‘VA’

    4.从表中选择出生日大于1990-01-01的顾客
    SELECT *
    FROM Customers
    WHERE birth_date > ‘1990-01-01’

    5.得到今年的订单
    SELECT *
    FROM Orders
    WHERE order_date >= ‘2019-01-01’