Wiley Beginning SQL Server 2005 Programming 978-0-7645-8433-6 사용자 설명서
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978-0-7645-8433-6
1
RDBMS Basics: What Makes
Up a SQL Ser ver Database?
What makes up a database? Data for sure. (What use is a database that doesn’t store anything?)
But a Relational Database Management System (RDBMS) is actually much more than data. Today’s
advanced RDBMSs not only store your data; they also manage that data for you, restricting what
kind of data can go into the system, and also facilitating getting data out of the system. If all you
want is to tuck the data away somewhere safe, you could use just about any data storage system.
RDBMSs allow you to go beyond the storage of the data into the realm of defining what that data
should look like, or the business rules of the data.
But a Relational Database Management System (RDBMS) is actually much more than data. Today’s
advanced RDBMSs not only store your data; they also manage that data for you, restricting what
kind of data can go into the system, and also facilitating getting data out of the system. If all you
want is to tuck the data away somewhere safe, you could use just about any data storage system.
RDBMSs allow you to go beyond the storage of the data into the realm of defining what that data
should look like, or the business rules of the data.
Don’t confuse what I’m calling the “business rules of data” with the more generalized business
rules that drive your entire system (for example, someone can’t see anything until they’ve logged
on, or automatically adjusting the current period in an accounting system on the first of the
month). Those types of rules can be enforced at virtually any level of the system. (These days, it’s
usually in the middle or client tier of an n-tier system). Instead, what we’re talking about here are
the business rules that specifically relate to the data. For example, you can’t have a sales order
with a negative amount. With an RDBMS, we can incorporate these rules right into the integrity of
the database itself.
rules that drive your entire system (for example, someone can’t see anything until they’ve logged
on, or automatically adjusting the current period in an accounting system on the first of the
month). Those types of rules can be enforced at virtually any level of the system. (These days, it’s
usually in the middle or client tier of an n-tier system). Instead, what we’re talking about here are
the business rules that specifically relate to the data. For example, you can’t have a sales order
with a negative amount. With an RDBMS, we can incorporate these rules right into the integrity of
the database itself.
This chapter provides an overview to the rest of the book. Everything discussed in this chapter
will be covered again in later chapters, but this chapter is intended to provide you with a roadmap
or plan to bear in mind as we progress through the book. Therefore, in this chapter, we will take a
high-level look into:
will be covered again in later chapters, but this chapter is intended to provide you with a roadmap
or plan to bear in mind as we progress through the book. Therefore, in this chapter, we will take a
high-level look into:
❑
Database objects
❑
Data types
❑
Other database concepts that ensure data integrity
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