98-364: MTA: Database Fundamentals :
Module2: Creating Database Objects :
Choose data types .
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 the kind of data that can go into the system, and facilitating getting data out of the system. An instance of an RDBMS such as SQL Server contains many objects. Object purists out there may quibble with whether Microsoft’s choice of what to call an object (and what not to) actually meets the normal definition of an object, but, for SQL Server’s purposes, the list of some of the more important database objects can be said to contain such things as:
- The database itself
- The transaction log
- Stored procedures
- User-defined functions
- Full-text catalogs
- User-defined data types
An RDBMS is designed to maintain data integrity in a transactional environment. This is accomplished through several mechanisms implemented through database objects. The most prominent of these objects are as follows:
Three categories of statements within SQL are used to define and manage a database and the objects contained therein, to control access to data and database functionality, and to manage the data in a database. Data Definition Language (DDL) encompasses the CREATE and ALTER statements, used to define database objects. Data Control Language (DCL) is used to manage security access and user privileges to data and database objects. Finally, Data Manipulation Language (DML) is the subset of SQL you will typically use most often. DML contains the SELECT , INSERT , UPDATE , and DELETE statements and several variations of these statements that you will use to populate tables with records, modify, remove, and read data values. The SELECT statement has several modifiers and additional commands and clauses you will use to do useful things with, and make sense of, the data stored in a database.
Thus The database is effectively the highest-level object that you can refer to within a given SQL Server. Most, but not all, other objects in a SQL Server are children of the database object.
A database is typically a group of constructs that include at least a set of table objects and, more often than not, other objects, such as stored procedures and views that pertain to the particular grouping of data stored in the database’s tables.
An RDBMS, such as SQL Server, may have multiple databases on just one server.
When you first load SQL Server, you start with at least four system databases:
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