返回结果:
LastName
FirstName
Address
City
Svendson
Tove
Borgvn 23
Sandnes
用OR运算子来查找"Persons"表中FirstName为”Tove”或者LastName为” Svendson”的数据
SELECT * FROM Persons WHERE firstname='Tove' OR lastname='Svendson'
返回结果:
LastName
FirstName
Address
City
Svendson
Tove
Borgvn 23
Sandnes
Svendson
Stephen
Kaivn 18
Sandnes
你也能结合AND和OR (使用括号形成复杂的表达式),如:
SELECT * FROM Persons WHERE (FirstName='Tove' OR FirstName='Stephen') AND LastName='Svendson'
返回结果:
LastName
FirstName
Address
City
Svendson
Tove
Borgvn 23
Sandnes
Svendson
Stephen
Kaivn 18
Sandnes
Between…And
用途：
指定需返回数据的范围
语法：
SELECT column_name FROM table_name WHERE column_name BETWEEN value1AND value2
例：“Persons”表中的原始数据
LastName
FirstName
Address
City
Hansen
Ola
Timoteivn 10
Sandnes
Nordmann
Anna
Neset 18
Sandnes
Pettersen
Kari
Storgt 20
Stavanger
Svendson
Tove
Borgvn 23
Sandnes
用BETWEEN…AND返回LastName为从”Hansen”到”Pettersen”的数据：
SELECT * FROM Persons WHERE LastName BETWEEN 'Hansen' AND 'Pettersen'
返回结果
LastName
FirstName
Address
City
Hansen
Ola
Timoteivn 10
Sandnes
Nordmann
Anna
Neset 18
Sandnes
Pettersen
Kari
Storgt 20
Stavanger
为了显示指定范围之外的数据，也可以用NOT操作符：
SELECT * FROM Persons WHERE LastName NOT BETWEEN 'Hansen' AND 'Pettersen'
返回结果
LastName
FirstName
Address
City
Svendson
Tove
Borgvn 23
Sandnes
Distinct
用途：
DISTINCT关键字被用作返回唯一的值
语法：
SELECT DISTINCT column-name(s) FROM table-name
解释：当column-name(s)中存在重复的值时，返回结果仅留下一个
例：
“Orders”表中的原始数据
Company
OrderNumber
Sega
3412
W3Schools
2312
Trio
4678
W3Schools
6798
用DISTINCT关键字返回Company字段中唯一的值：
SELECT DISTINCT Company FROM Orders
返回结果
Company
Sega
W3Schools
Trio
Order by
用途：
指定结果集的排序
语法：
SELECT column-name(s) FROM table-name ORDER BY { order_by_expression [ ASC | DESC ] }
解释：指定结果集的排序，可以按照ASC(递增方式排序，从最低值到最高值)或者DESC(递减方式排序，从最高值到最低值)的方式进行排序，默认的方式是ASC
例：
“Orders”表中的原始数据:
Company
OrderNumber
Sega
3412
ABC Shop
5678
W3Schools
2312
W3Schools
6798
按照Company字段的升序方式返回结果集：
SELECT Company, OrderNumber
