http://www.databasecompare.com/faq/knowledge_base.html knowledge_base http://www.databasecompare.com/What-is-data-database-(DB)-DBMS-and-DBS.html In computer science, data is anything in a form suitable for use with a computer, and it's often distinguished from programs.A database is a collection of information which is organized so that it can easily be accessed, managed, and updated.Database management system (DBMS) is a computer software program that is designed as the means of managing all databases that are currently installed on a system hard drive or network.Database system is a system to achieve an organized, store a large number of dynamical associated data, facilitate for multi-user accessing to computer hardware, software and data, that it is a computer system with database technology. http://www.databasecompare.com/What-is-index-(database).html In database, index is a data structure, which orders data of one or more columns in database table.It can be created by using one or more columns of a database table, providing the basis for both rapid random look ups and efficient access of ordered records.We can use index to access the specific information quickly in database table. http://www.databasecompare.com/What-is-field.html In database, rows or lines of a table have special names. Each line is called a "field". Each field has a special subject. Relational databases arrange data as sets of database records, also called rows. Each record consists of several fields; the fields of all records form the columns. And in object-oriented programming, field is also called date member, and it is the data encapsulated within a class or object. http://www.databasecompare.com/What-is-primary-key-and-unique-key.html A primary key is a special case of unique key. Primary keys may consist of a single attribute or multiple attributes in combination. And it’s unique, what the difference from the unique key is the primary key cannot be NULL, and primary keys must be defined by using another syntax. Depending on its design, a table may have arbitrarily many unique keys but at most one primary key.A unique key must uniquely identify all possible rows that exist in a table and not only the currently existing rows. It can either be a normal attribute that is guaranteed to be unique (such as Social Security Number in a table with no more than one record per person) or it can be generated by the DBMS (such as a globally unique identifier, or GUID, in Microsoft SQL Server). http://www.databasecompare.com/What-is-data-model.html A data model in software engineering is an abstract model that describes how data is represented and accessed.Data models formally define data elements and relationships among data elements for a domain of interest. Data model explicitly determines the meaning of data, which in this case is known as structured data. Typical applications of data models include database models, design of information systems, and enabling exchange of data. Usually data models are specified in a data modeling language. A data model can be sometimes referred to as a data structure, especially in the context of programming languages. http://www.databasecompare.com/What-is-foreign-key.html In relational databases, a foreign key is a field in a relational table that matches the primary key column of another table. The foreign key can be used to cross-reference tables. The columns in the referencing table must be the primary key or other candidate keys in the referenced table. Each foreign key is enforced independently by the database system. http://www.databasecompare.com/What-is-role.html When several users need to perform the similar actions in a particular database (no corresponding Windows User Group in this case), they will be able to add a database role. The database role can specify the group of database users which they can access the same database objects. http://www.databasecompare.com/What-is-date-type.html In a broad sense, a data type can be defined as a set of values and the allowable operations on those values. In programming languages, date type is an attribute of date. Date type can tells the computer (and the programmer) something about the kind of data it is. Almost all programming languages explicitly include the notion of data type, though different languages may use different terminology. Most programming languages also allow the programmer to define additional data types, usually by combining multiple elements of other types and defining the valid operations of the new data type. http://www.databasecompare.com/What-is-view-(database).html From the user's point of view, a view (database) can view the data in a special angle. From database theory, a view (database) is a virtual table, which consists of a stored query accessible composed of the result set of a query. From inside of the database system, the view composes with the data of one or more tables. From external database system, the view is just like a table, and it can be operated as a table, such as query, insert, modify or delete and so on. http://www.databasecompare.com/What-is-data-storage.html Data storage is the temporary file generated by data stream in processing or the information need to be found in processing. Recording data with some formats in the computer internal or external storage media. Data storage should have a special name which could reflect the characteristics of information. Data stream reflects the flowing data in system, it shows the characteristics of dynamic data; data storage reflects the static data in system, it shows the characteristics of static data. http://www.databasecompare.com/What-is-stored-procedure.html In relational database system, stored procedure is precompiled database queries that improve the security, efficiency and usability of database client/server applications. Developers implement it with the specified a stored procedure name and parameters (if the stored procedure with parameters). Storage process is a process which is controlled by the flow and the statements of writing SQL. This process is stored in the database server by optimized and the compiled. Applications just need call it in used. http://www.databasecompare.com/What-is-trigger.html In database, trigger is a stored procedure that may be configured to automatically execute when certain events take place. Triggers can restrict access to specific data, perform logging, or audit data modifications. Each trigger is associated with a single table and is set to fire when records are inserted into, updated in, or deleted from that table. Triggers offer database developers and administrators a tremendous degree of flexibility. They are, quite simply, stored procedures that may be configured to automatically execute when certain events take place. http://www.databasecompare.com/What-is-static-function.html A static function is a function whose scope is limited to the current source file. Scope refers to the visibility of a function or variable. If the function or variable is visible outside of the current source file, it is said to have global, or external, scope. If the function or variable is not visible outside of the current source file, it is said to have local, or static, scope. http://www.databasecompare.com/What-is-extern-function.html An extern function is to indicate the existence of, and the type of, a global variable or function. A global variable, or a global function, is one that is available to all C modules (a single C module is typically a single .c file). An extern is something that is defined externally to the current module. http://www.databasecompare.com/What-is-cursor-(database).html In database programs, cursors are database objects used to traverse the results of an SQL query. Each cursor has a name of its own. Developers can get record from cursor with SQL query one by one, and assign them to major variable for further process with host language. http://www.databasecompare.com/What-is-full-text-search.html Full text search is a technique for retrieving the files matching the retrieval keys. It's a computer program by scanning a computer-stored document or database. In a full text search, the search engine examines all of the words in every stored document as it tries to match search words supplied by the user. http://www.databasecompare.com/What-is-database-transaction.html In database, a database transaction is a logical unit of database operations which are executed as a whole to process user requests for retrieving data or updating the database.Transaction should have four properties: atomic, consistent, isolated and durable. These properties of database transactions are often referred to by the acronym ACID. http://www.databasecompare.com/What-is-index-architecture.html In database,index architectures can be classified as clustered or non-clustered.A non-clustered index is structured in a way that doesn't correspond to the order of the actual data records. It resembles the words index at the back of a book.Clustering re-orders the data block in the same order as the index, hence it is also an operation on the data storage blocks as well as on the index. http://www.databasecompare.com/What-is-T-SQL-(Transact-SQL).html Transact-SQL is proprietary extension SQL from Sybase and Microsoft that add several features to the Structured Query Language (SQL) including transaction control, exception and error handling, row processing, and declared variables. Microsoft's SQL Server and Sybase's SQL server support T-SQL statements. All applications that communicate with SQL Server do so by sending Transact-SQL statements to the server, regardless of an application's user interface. http://www.databasecompare.com/What-is-transaction-log.html In database, transaction log is also called database log or binary log, and it's a record of actions. It can record any action by the database and store the recording results in a separate file. The location of the SQL Server transaction log is configured at the same time as the database is created. When creating a database, the location of the SQL Server transaction log is specified as well as other options associated with the transaction log. http://www.databasecompare.com/What-is-information-system.html Information system is a system which could deal with the data with all kinds of methods, including data inserted into the database, modify data from the database, and access the data to browse from database and so on. In a narrow sense, the term information system (or computer-based information system) which is referred to in the specific application software is used to store data records in a computer system and automate some of the information-processing activities of the organization. Computer-based information systems are in the field of information technology. The discipline of business process modeling which describes the business processes is supported by information systems. http://www.databasecompare.com/What-is-rule-(database).html In database, rules are the requirements and restrictions for columns which are stored in the table or value of user-defined data type. Rule is independent database object with separate stored. Rule is independent with the table or user-defined data type. That is to say, when we delete or modify the table or user-defined data type, it doesn't affect the corresponding rule. Rules and constraints can be used at the same time. http://www.databasecompare.com/What-is-Database-Integrity.html In database, database integrity is accuracy and compatibility of data.The database integrity is on the faith of many integrity constraints, so that is, designing complete database integrity is designing a complete database integrity constraint. Database integrity constraint can be achieved through the DBMS or application, and it is based on integrity constraint of DBMS as a part of mode to be stored in database. With achieving the integrity constraint of DBMS, we could design it according to the steps of designing database. And by the application software to achieve the integrity of the database are included in the application of software design. http://www.databasecompare.com/What-is-data-backup-and-data-recovery.html Data backup is an insurance plan. It is defined as a system in operation to avoid errors or system failures, and data lossing, storing the copy of whole or in part from the application host data set or array of hard disk to other storage medium. Data recovery is a system in operation to rescue and recover the lost data in database from data copy. http://www.databasecompare.com/What-is-lock-(database).html In database, a lock is used to access a database concurrently for multiple users. This prevents data from being corrupted or invalidated when multiple users try to write to the database. Any single user can only modify those database records (that is, items in the database) to which they have applied a lock that gives them exclusive access to the record until the lock is released. http://www.databasecompare.com/What-is-job-manager.html In SQL Server, job is defined as a multistep operation. Each step is a Transact-SQL as a task possibly. Job is a typical task planning and automate tasks. Database backup and recovery, data copy, data import / export, etc. can be defined as Job, and then in the planning time auto-complete with SQL Server Agent. http://www.databasecompare.com/What-is-alarm-manager-(database).html In SQL Server, an alert is defined as alarm manager. It will alarm automatically when some particular events occur. When the alarm is triggered, the notification by e-mail or paging operators, that letting system operator to know what is event, such as lack of database space or transaction log is full.