题目内容
如果要在WHERE子句中判断某元组的某一字段（假设是FieldName）是否为空值，可以使用 FieldName IS NULL 语法，也可以使用 FieldName = NULL 语法。
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假设某同学年龄为30岁(Sage=30)，另一个同学年龄为20岁(Sage=20)，则他们都不满足 Sage BETWEEN 20 AND 30.
可以为SELECT子句中的目标列表达式指定别名，一种方法是直接在目标列表达式后加上空格和别名。
Please fill in the blanks according to hints given in brackets.(1.气候变化）may be a big problem, but there are many little things we can do to(2.影响它）. If we try, most of us can (3.出一份力)to reduce the amount of (4.温室气体)that we (5.排放) the atmosphere. Many greenhouse gases (6. 来自)things we do every day. As we have learned, these greenhouse gases (7. 困锁能量) in the atmosphere and make the Earth warmer.Driving a car or (8.用电）is not wrong. We just have to (9.动动脑子）it. Some people use less energy by (10.拼车）. For example, four people can ride together in one car (11. 而不是）driving four cars to work. (12.为什么不）try to do something to help make the planet a better place?
Please fill in the blanks according to hints given in brackets.Save ElectricityWhenever we use electricity, we put (1.温室气体）into the air. By (2.关闭）lights, the television, and the computer when you are (3.用完）them, you can help a lot.If you’re leaving your computer for a while, put it on (4.待机状态）. You’ll be able to (5.重启）it quickly, and it’ll take less energy than (6.关闭）it down and then restarting it.Bus, Bike and WalkYou can save energy by sometimes taking the bus, riding a bike, or simply walking. And now the (7.共享自行车）provide a lot of convenience.Plant Trees(8.植树)is fun and a great way to reduce greenhouse gases. Trees (9.吸收)carbon dioxide from the air.RecycleNow many cities have realized practice (10.垃圾分类）for recycling. When you do the (11.回收）, you send less (12.垃圾）to the landfill and you help save (13.自然资源）, like wood, oil, and (14.金属）.
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