1.What is a transaction and what are ACID properties?
Ans: A transaction is a logical unit of work in which, all the steps must be performed or none.
ACID stands for Atomicity, Consistency, Isolation, Durability. These are the properties of a transaction. For more information and explanation of these properties, see SQL Server books online or any RDBMS fundamentals text book.
2.What is non-key attributes?
Ans: The attributes other than the primary key attributes in a table/relation are called non-key attributes.
3.What is a NULL value?
Ans: A null value is used to indicate the absence of a value. It is not a zero or blank character. Null cannot be compared to any other value.
4.Why do we use is null, is not null operators?
Ans: If it is needed to find out the rows, then we have to use is null operator so that we get the rows whose one of the column values is null and in order to retrieve the rows which does not have null as any column value.
5.What are aggregate functions / column functions?
Ans: A SQL column function takes an entire column of data as its arguments and produces a single data item that summarizes the column.
Sum(), avg(), min(), max(), count() and count(*)
6.What is a tablespace?
Ans: 1.Tablespace are a mechanism or a means by which logical objects such as tables, indexes, and views are mapped to a specific data file.
2.A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together.
7.What is SYSTEM tablespace and when is it created?
Ans: Every Oracle database contains a tablespace named SYSTEM, which is automatically created when the database is created. The SYSTEM tablespace always contains the data dictionary tables for the entire database.
8.Explain the relationship among database, tablespace and data file ?
Ans: Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace.
9.What is schema?
Ans: A schema is collection of database objects of a user.
Ans: A transaction is a logical unit of work in which, all the steps must be performed or none.
ACID stands for Atomicity, Consistency, Isolation, Durability. These are the properties of a transaction. For more information and explanation of these properties, see SQL Server books online or any RDBMS fundamentals text book.
2.What is non-key attributes?
Ans: The attributes other than the primary key attributes in a table/relation are called non-key attributes.
3.What is a NULL value?
Ans: A null value is used to indicate the absence of a value. It is not a zero or blank character. Null cannot be compared to any other value.
4.Why do we use is null, is not null operators?
Ans: If it is needed to find out the rows, then we have to use is null operator so that we get the rows whose one of the column values is null and in order to retrieve the rows which does not have null as any column value.
5.What are aggregate functions / column functions?
Ans: A SQL column function takes an entire column of data as its arguments and produces a single data item that summarizes the column.
Sum(), avg(), min(), max(), count() and count(*)
6.What is a tablespace?
Ans: 1.Tablespace are a mechanism or a means by which logical objects such as tables, indexes, and views are mapped to a specific data file.
2.A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together.
7.What is SYSTEM tablespace and when is it created?
Ans: Every Oracle database contains a tablespace named SYSTEM, which is automatically created when the database is created. The SYSTEM tablespace always contains the data dictionary tables for the entire database.
8.Explain the relationship among database, tablespace and data file ?
Ans: Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace.
9.What is schema?
Ans: A schema is collection of database objects of a user.
Schema is the over all design of the database
Schema basically 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.
10.What are Schema Objects?
Ans: Schema objects are the logical structures that directly refer to the database's data. Schema objects include tables, views, sequences, synonyms, indexes, clusters, database triggers, procedures, functions packages and database links.
10.What are Schema Objects?
Ans: Schema objects are the logical structures that directly refer to the database's data. Schema objects include tables, views, sequences, synonyms, indexes, clusters, database triggers, procedures, functions packages and database links.
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3 comments:
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