SqlServer系列：Select基本语句

<SELECT statement> ::=  
    [WITH  [,...n]]
    <query_expression> 
    [ ORDER BY { order_by_expression | column_position [ ASC | DESC ] } 
  [ ,...n ] ] 
    [ ] 
    [ OPTION (  [ ,...n ] ) ] 
<query_expression> ::= 
    { <query_specification> | ( <query_expression> ) } 
    [  { UNION [ ALL ] | EXCEPT | INTERSECT }
        <query_specification> | ( <query_expression> ) [...n ] ] 
<query_specification> ::= 
SELECT [ ALL | DISTINCT ] 
    [TOP ( expression ) [PERCENT] [ WITH TIES ] ] 
    < select_list > 
    [ INTO new_table ] 
    [ FROM {  } [ ,...n ] ] 
    [ WHERE  ] 
    [  ] 
    [ HAVING  ] 

SELECT * FROM [dbo].[Product]

SELECT [ProductID],[ProductName] FROM [dbo].[Product]

SELECT 
    [ProductID],
    [ProductName],
    [UnitPrice] * 2 AS DoubleUnitPrice
FROM [dbo].[Product]

SELECT TOP [n | PERCENT] FROM table_name

SELECT TOP (10) * FROM [dbo].[Product]

SELECT TOP (10) PERCENT * FROM [dbo].[Product]