SQL语句大全

1.检索数据

检索student_name单个列： 
SELECT  student_name 
FROM Student;

检索多个列：
SELECT student_id,student_name,student_age 
FROM Student;

检索所有列：
SELECT * 
FROM Student;
最好不要用"*"代替字段，这是一个低效的方法，因为DBMS要耗时把"*"转为字段

2.排序检索数据

按一个列排序检索：
SELECT student_name 
FROM Student  
ORDER BY student_name;

按多个列排序检索：
SELECT student_id,student_name,student_age 
FROM Student 
ORDER BY student_name,student_id;

按位置排序：
SELECT student_id,student_name,student_age 
FROM Student 
ORDER BY 2,3;

3.过滤数据

检查单个值：
SELECT student_id,student_name,student_age 
FROM Student 
WHERE student_age<22;

不匹配检查：
SELECT student_id,student_name,student_age 
FROM Student 
WHERE student_name <> 'Bruce';
where子句中少用 <> 操作符，它容易引起全表扫描

范围值检查：
SELECT student_id,student_name,student_age 
FROM Student 
WHERE student_age  BETWEEN 20 AND 22;
BETWEEN效率比IN高，能用BETWEEN就不要用IN

空值检查：
SELECT student_id,student_name,student_city,student_age,student_email 
FROM Student  
WHERE student_age IS NULL; 
NULL值判断，要全表扫描，也应避免

4.操作符数据过滤

AND操作符：
SELECT  student_id, student_name,student_city,student_age,student_email,
student_class 
FROM Student 
WHERE student_class = '2班' AND student_age<=20;

OR操作符：
SELECT student_id, student_name,student_city,student_age,student_email,
student_class 
FROM Student 
WHERE student_class = '2班' OR  student_class='1班';
where子句中用or来连接条件，可以用UNION ALL

IN操作符：
SELECT  student_id,student_name,student_city,student_age,
student_email,student_class 
From Student  
WHERE student_class IN('1班','2班')  
ORDER BY student_id;
易导致全表扫描，可以用表联结替换

NOT操作符（否定他之后的任何条件）：
SELECT student_id,student_name,student_city,student_age,student_email,     student_class 
From Student  
WHERE  NOT student_class='1班' 
ORDER BY student_id;

5.通配符过滤

百分号通配符：
SELECT student_id,student_name,student_city,  student_age,student_email 
From Student  
WHERE student_name LIKE 'B%' 
ORDER BY student_id;

下划线通配符：
SELECT * 
FROM Student 
WHERE student_id LIKE '10_9'; 

方括号通配符：
SELECT student_name 
FROM Student 
WHERE student_name LIKE '[A]%' 
ORDER BY student_name;

6.计算字段

拼接字段：
SELECT student_name || '(' ||student_age||')'  
FROM Student 
ORDER  BY student_name;

RTRIM()函数，去掉右边所有空格：
SELECT RTRIM(student_name) || '(' || student_age || ')'  
FROM Student 
ORDER BY student_name;

使用别名：
SELECT RTRIM(student_name) || '(' || student_age || ')'  AS student_name1 
FROM Student 
ORDER BY student_name;

执行算数字段：
SELECT student_id,student_age,student_age*student_id AS num 
FROM Student;

7.使用函数处理数据

文本处理函数：
SELECT student_name ,UPPER(student_name) AS student_name1 
FROM Student 
ORDER BY student_name;

AVG()函数，返回所有列的平均值：
SELECT AVG(student_age) AS student_age1 
FROM Student;

COUNT()函数：1.使用COUNT(*) 对表中行的数目进行计数，包含空值NULL与非空值。2.使用COUNT()对特定列中有值的行进行计数，忽略NULL值
SELECT COUNT(*) AS student_id 
FROM Student; 
不带任何条件的count会引起全表扫描，要避免

MAX()函数：返回指定列最大值，要求指定列名，忽略NULL值的行。
SELECT MAX( student_age) AS student_age 
FROM Student;

MIN()函数：
SELECT MIN( student_age) AS student_age 
FROM Student;

SUM()函数：
SELECT SUM(student_age) AS student_age1 
FROM Student 

8.数据分组

创建分组：
SELECT student_id,COUNT(*) AS student_id1 
FROM Student 
GROUP BY student_id;

9.子查询

使用子查询过滤：
SELECT student_id,student_name,student_city 
FROM Student 
WHERE student_id 
IN (SELECT teacher_id FROM Teacher WHERE student_name 
IN (SELECT student_name FROM Person WHERE student_id = '1001'));

作为计算字段使用子查询：
SELECT student_id,student_name,student_city,(SELECT COUNT(*) 
FROM Student 
WHERE Student.student_id = Person.student_id) AS orders FROM Person; 

10.联结表

创建联结:
SELECT student_name,teacher_name,teacher_city 
FROM Student,Teacher 
WHERE Student.student_id=Teacher.teacher.id; 

内部联结：
SELECT student_name,teacher_name,teacher_city 
FROM Student
INNER JOIN ON Student.student_id=Teacher.teacher_id;

联结多个表：
SELECT Student.student_name,teacher_name,teacher_city,Person.student_city 
FROM Person, Teacher,Student 
WHERE Student.student_id = Teacher.teacher_id AND Teacher.teacher_id = Person.student_id;

11.插入数据

数据插入：
INSERT INTO Student(student_id,student_name,student_city,student_age,student_email)  
VALUES( '1006' , 'MJ' ,'上海' , NULL , '[email protected]'); 

插入部分行：
INSERT INTO Student(student_id,student_name,student_city,student_age) 
VALUES( ' 1011' , 'KUFU' ,'北京' ,21);

插入检索出的数据：
INSERT INTO  Person(student_id,student_name,student_city,student_age)  
SELECT student_id,student_name,student_city,student_age 
FROM Student 
WHERE student_id='1006';

复制数据：从一个表复制到另一个表（运行中创建的表）：
CREATE TABLE StudentCopy AS
SELECT *
FROM Student;

12.更新和删除数据

更新表中特定行：
UPDATE Student SET student_email='[email protected]'
WHERE student_id='1001';

删除表中特定行：
DELETE FROM Student 
WHERE student_id='1001';

13.创建表

create table Student1
(
          student_id           number(10),            
          student_name         char( 10 ),            
          student_city         char( 10 ),            
          student_age          char( 10 ),            
          student_email        char( 20 ));

增加列：
ALTER TABLE Student 
ADD student_class char(50);

删除列：
ALTER TABLE Student1 
DROP COLUMN student_phone;

重命名表：
rename Student1 to Student;

删除表：
DROP TABLE student;

14.试图
创建视图：CREATE VIEW 只能用于创建不存在的试图

用试图简化复杂的联结：
CREATE VIEW ProduceStudent AS 
SELECT teacher_name
FROM Student,Teacher,Person 
WHERE Student.student_id=Teacher.teacher_id 
AND Person.student_id=Student.student_id;

用试图重新格式化检索出的数据:
CREATE VIEW StudentLocations 
AS SELECT RTRIM(student_name) ||  '（'|| RTRIM（student_city）|| ')'  
AS student_title 
FROM Student;

检索出数据：
SELECT * 
FROM StudentLocations;

15.管理事物

DELETE FROM Student;
ROLLBACK;

COMMIT:DELETE OrderItems 
       WHERE order_num = 12345 ;
       DELETE Orders 
       WHERE order_num = 12345 ;
       COMMIT ;  

创建保留点：SAVEPOINT delete1;
          ROLLBACK TO delete1;