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数据库知识点

发布时间:2016-04-06 13:00:04
WHY SQL?1.SQL is a very-high-level language, in which the programmer is able to avoid specifying a lot of data-manipulation details that wou ...
WHY SQL?

(1)SELECT - FROM - WHERE statements 

  SELECT ... (desired attributes)

  From ... (one or more tables)

  WHERE ...( condition about tuples of the tables)

EX: Using Beers(name, manf), what beers are made by Busch?

SELECT name,FROM Beers,WHERE manf = 'Busch'

We may specify desc for descending order or asc for ascending order, for each attribute; ascending order is the default.

Example:  order by customer_name desc

 EX:From Sells(bar, beer, price), find the average price of Bud:

SELECT AVG(price)FROM SellsWHERE beer = ‘Bud’;

原标题:数据库知识点

关键词:数据库

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