SQL语法手册.doc

文档介绍：SQL语法手册Select
用途:
从指定表中取出指定的列的数据
语法:
 
SELECT column_name(s) FROM table_name
 
解释:
从数据库中选取资料列,并允许从一或多个资料表中,选取一或多个资料列或资料行。SELECT 陈述式的完整语法相当复杂,但主要子句可摘要为:
SELECT select_list
[ INTO new_table ]
FROM table_source
[ WHERE search_condition ]
[ GROUP BY group_by_expression ]
[ HAVING search_condition ]
[ ORDER BY order_expression [ ASC | DESC ] ]
例:
“Persons”表中的数据有
LastName
FirstName
Address
City
Hansen
Ola
Timoteivn 10
Sandnes
Svendson
Tove
Borgvn 23
Sandnes
Pettersen
Kari
t 20
Stavanger
选出字段名” LastName”、” FirstName”的数据
SELECT LastName,FirstName FROM Persons
返回结果:
LastName
FirstName
Hansen
Ola
Svendson
Tove
Pettersen
Kari
选出所有字段的数据
SELECT * FROM Persons
返回结果:
 
LastName
FirstName
Address
City
Hansen
Ola
Timoteivn 10
Sandnes
Svendson
Tove
Borgvn 23
Sandnes
Pettersen
Kari
t 20
Stavanger
 
 
 
Where
用途:
被用来规定一种选择查询的标准
语法:
SELECT column FROM table WHERE column condition value
下面的操作符能被使用在WHERE中:
=,<>,>,<,>=,<=,BETWEEN,LIKE
注意: 在某些SQL的版本中不等号< >能被写作为!=
解释:
SELECT语句返回WHERE子句中条件为true的数据
例:
从” Persons”表中选出生活在” Sandnes”的人
SELECT * FROM Persons WHERE City='Sandnes'
"Persons" 表中的数据有:
LastName
FirstName
Address
City
Year
Hansen
Ola
Timoteivn 10
Sandnes
1951
Svendson
Tove
Borgvn 23
Sandnes
1978
Svendson
Stale
Kaivn 18
Sandnes
1980
Pettersen
Kari
t 20
Stavanger
1960
返回结果:
LastName
FirstName
Address
City
Year
Hansen
Ola
Timoteivn 10
Sandnes
1951
Svendson
Tove
Borgvn 23
Sandnes
1978
Svendson
Stale
Kaivn 18
Sandnes
1980
 
 
 
And & Or
用途:
在WHERE子句中AND和OR被用来连接两个或者更多的条件
解释:
AND在结合两个布尔表达式时,只有在两个表达式都为 TRUE 时才传回 TRUE
OR在结合两个布尔表达式时,只要其中一个条件为 TRUE 时,OR便传回 TRUE
例:
"Persons" 表中的原始数据:
LastName
FirstName
Address
City
Hansen
Ola
Timoteivn 10
Sandnes
Svendson
Tove
Borgvn 23
Sandnes
Svendson
Stephen
Kaivn 18
Sandnes
用AND运算子来查找"Persons" 表中FirstName为”Tove”而且LastName为” Svendson”的数据
SELECT * FROM Persons
WHERE FirstName='Tove'
AND LastName=