Can objects of the same schema reside in different table spaces?
Yes we can objects of the same schema reside in different table space. Schema objects can stored in different tablespace and a tablespace can contained one or more schema objects data.Reply
What is schema?
Schema bassically Pronounce skee-ma, It is the structure of a database system,It described in a formal language supported by the database management system (DBMS). In the RDBMS (Relational database System) , the schema defines the tables, the fields in each table, and the Schemas are generally stored in a data dictionary . Even a schema is defined in text database language , the term is often used to refer to a graphical depiction of the database structure. Reply
Explain the relationship among database, tablespace and data file.
Database : Database is the Collection of data is called database.
Table Space : The table space ismany use for storing the data in the database. When a database is created two table spaces are created.
i) System Table Space : This data file stores
all the tables related to the system and dba tables.
ii) User Table Space : This data file stores all the user related tables. We should have separate table spaces for storing the tables and indexes so that the access is fast.
Data Files : Every Oracle Data Base has one or more physical data files. They store the data for the database. Every data-file is associated with only one database. Once the Data file is created the size cannot change. To increase the size of the database to store more data we have to add data file. Reply
What is SYSTEM tablespace and when is it created?
Every ORACLE database have a table space which name is SYSTEM . when the database is created taht a time its also automatically created. The SYSTEM tablespace always contains the data dictionary tables for the entire database.Reply
What are the components of logical database structure of Oracle database?
The Logical Database Structure of an Oracle include :
> The schema objects,
> Data blocks,
> Segments and
> schema objects : means table, index, synonyms, sequences etc.
> Data blocks : are the smallest part of the oracle database defined by DB_BLOCK_SIZE parameter.
> Extent : A group of data blocks forms an extent.
> Segments : An extents groups tends to segments,
> Table space : lastly a group of segment forms a tablespace.Reply
What are the components of physical database structure of Oracle database?
Physical components of oracle database are:
> Control files,
> Redo log files and
> Control file : control file is basicaly a type of file .Its read in the mount state of database. control file is a small binary file which records the physical structure of database which includes
* Database name
* names and locations of datafiles and online
redo log files.
* timestamp of database creation
* check point information
* current log sequence number.
Redo log files : Redo log files usually use for the saving to the files. This files saves all the changes that are made to the database as they occur. This plays a great role in the database recovery.
Datafiles : Datafiles are the physicalfiles which stores data of all logical structure.Reply
What is SQL?
SQL is a bassically standard language for accessing and manipulating databases. Its is defines as :
> SQL stands for Structured Query Language
> SQL lets you access and manipulate databases
> SQL is an ANSI (American National Standards Institute) standard.
SQL have a many properties, It can do :
> SQL can execute queries against a database.
> SQL can retrieve data from a database.
> SQL can insert records in a database.
> SQL can update records in a database.
> SQL can delete records from a database.
> SQL can create new databases.
> SQL can create new tables in a database.
> SQL can create stored procedures in a database.
> SQL can create views in a database.
> SQL can set permissions on tables, procedures,
What is Index?
An index is a physical structure containing pointers to the data. Indices are created in an existing table to locate rows more quickly and efficiently. It is possible to create an index on one or more columns of a table, and each index is given a name. The users cannot see the indexes, they are just used to speed up queries. Effective indexes are one of the best ways to improve performance in a database application
. A table scan happens when there is no index available to help a query. In a table scan SQL Server examines every row in the table to satisfy the query results. Table scans are sometimes unavoidable, but on large tables, scans have a terrific impact on performance.Reply
What is View?
A simple view can be thought of as a subset of a table. It can be used for retrieving data, as well as updating or deleting rows. Rows updated or deleted in the view are updated or deleted in the table the view was created with. It should also be noted that as data in the original table changes, so does data in the view, as views are the way to look at part of the original table. The results of using a view are not permanently stored in the database. The data accessed through a view is actually constructed using standard T-SQL select command and can come from one to many different base tables or even other views.Reply
What is Trigger?
A trigger is a SQL procedure that initiates an action when an event (INSERT, DELETE or UPDATE) occurs. Triggers are stored in and managed by the DBMS.Triggers are used to maintain the referential integrity of data by changing the data in a systematic fashion. A trigger cannot be called or executed; the DBMS automatically fires the trigger as a result of a data modification to the associated table. Triggers can be viewed as similar to stored procedures in that both consist of procedural logic that is stored at the database level. Stored procedures, however, are not event-drive and are not attached to a specific table as triggers are. Stored procedures are explicitly executed by invoking a CALL to the procedure while triggers are implicitly executed. In addition, triggers can also execute stored procedures.
Nested Trigger: A trigger can also contain INSERT, UPDATE and DELETE logic within itself, so when the trigger is fired because of data modification it can also cause another data modification, thereby firing another trigger. A trigger that contains data modification logic within itself is called a nested trigger.Reply