转自：http://ilonng.blog.sohu.com/130335741.html
oracle的number类型是一种软件数据类型，在oracle软件本身中实现，我们不能使用固有硬件操作将两个number类型相加，这要在软件中模拟，number 类型的内部编码是2。oracle存储一个数的时，会存储尽可能少的内容来表示这个数，为此它会存储有效数字、用于指定小数点位置的一个指数，以及有关数值符号的信息（正或者负）。因此，数中包含的有效数字越多，占用的存储空间就越大。
oracle底层存储number类型采用下面的这种形式：
sign bit/exponent,digit1,digit2,…,digit20
sign bit/exponent为标志位，digit1...digit20为数值位，可见number最多占据21个字节。
一个数是可以使用科学计算法来正确表示的，如10=1*power(10,1)，-101=-1.01*power(10,2)，0.2=2*power(10,-1)。oracle就是通过这个原理来存储数据，它将任何一个它可以表示的数据转换成一个符号位、一个指数、一个有效数来存储，举个例子，123在oracle中是这样来存储的，+(1.23*power(100,1))，即它是以100为科学计算法的指数基数，为什么这样以及怎么来存储，请看下面。
存储� ......
Exam Number/Code : 1z0-047
Exam Name : Oracle Database SQL Expert
Questions and Answers : 278 Q&As
Update Time: 2010-04-15
1. Which two statements are true regarding the execution of the correlated subqueries? (Choose two.)
A. The nested query executes after the outer query returns the row.
B. The nested query executes first and then the outer query executes.
C. The outer query executes only once for the result returned by the inner query.
D. Each row returned by the outer query is evaluated for the results returned by the inner query.
Answer: AD
2. View the Exhibit and examine the description of the EMPLOYEES table.
Your company decided to give a monthly bonus of $50 to all the employees who have completed five years in the
company. The following statement is written to display the LAST_NAME, DEPARTMENT_ID, and the total annual
salary:
SELECT last_name, department_id, salary+50*12 "Annual Compensation"
from employees
WHERE MONTHS_BETWEEN(SYSDATE, hire_date)/1 ......
Exam Number/Code : 1z0-047
Exam Name : Oracle Database SQL Expert
Questions and Answers : 278 Q&As
Update Time: 2010-04-15
1. Which two statements are true regarding the execution of the correlated subqueries? (Choose two.)
A. The nested query executes after the outer query returns the row.
B. The nested query executes first and then the outer query executes.
C. The outer query executes only once for the result returned by the inner query.
D. Each row returned by the outer query is evaluated for the results returned by the inner query.
Answer: AD
2. View the Exhibit and examine the description of the EMPLOYEES table.
Your company decided to give a monthly bonus of $50 to all the employees who have completed five years in the
company. The following statement is written to display the LAST_NAME, DEPARTMENT_ID, and the total annual
salary:
SELECT last_name, department_id, salary+50*12 "Annual Compensation"
from employees
WHERE MONTHS_BETWEEN(SYSDATE, hire_date)/1 ......
Exam Number/Code : 1z0-047
Exam Name : Oracle Database SQL Expert
Questions and Answers : 278 Q&As
Update Time: 2010-04-15
1. Which two statements are true regarding the execution of the correlated subqueries? (Choose two.)
A. The nested query executes after the outer query returns the row.
B. The nested query executes first and then the outer query executes.
C. The outer query executes only once for the result returned by the inner query.
D. Each row returned by the outer query is evaluated for the results returned by the inner query.
Answer: AD
2. View the Exhibit and examine the description of the EMPLOYEES table.
Your company decided to give a monthly bonus of $50 to all the employees who have completed five years in the
company. The following statement is written to display the LAST_NAME, DEPARTMENT_ID, and the total annual
salary:
SELECT last_name, department_id, salary+50*12 "Annual Compensation"
from employees
WHERE MONTHS_BETWEEN(SYSDATE, hire_date)/1 ......
Exam Number/Code : 1z0-047
Exam Name : Oracle Database SQL Expert
Questions and Answers : 278 Q&As
Update Time: 2010-04-15
1. Which two statements are true regarding the execution of the correlated subqueries? (Choose two.)
A. The nested query executes after the outer query returns the row.
B. The nested query executes first and then the outer query executes.
C. The outer query executes only once for the result returned by the inner query.
D. Each row returned by the outer query is evaluated for the results returned by the inner query.
Answer: AD
2. View the Exhibit and examine the description of the EMPLOYEES table.
Your company decided to give a monthly bonus of $50 to all the employees who have completed five years in the
company. The following statement is written to display the LAST_NAME, DEPARTMENT_ID, and the total annual
salary:
SELECT last_name, department_id, salary+50*12 "Annual Compensation"
from employees
WHERE MONTHS_BETWEEN(SYSDATE, hire_date)/1 ......
服务器启动的过程
Oracle数据服务器的常规启动过程:
1、启动TNS监听 C:\Documents and Settings\Administrator>lsnrctl start
2、启动Oracle Services C:\Documents and Settings\Administrator>net start OracleServiceOrcl
服务器启动的8种
1、startup nomount 非安装启动，这种方式启动下可执行：重建控制文件、重建数据库 读取init.ora文件，启动instance，即启动SGA和后台进程，这种启动只需要init.ora文件。
2、startup mount dbname 安装启动，这种方式启动下可执行： 数据库日志归档、数据库介质恢复、使数据文件联机或脱机， 重新定位数据文件、重做日志文件。执行“nomount”，然后打开控制文件，确认数据文件和联机日志文件的位置，但此时不对数据文 ......
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