DBMS Questions(71-80)

71.What is the difference between SQL and SQL Server ?

SQLServer is an RDBMS just like oracle,DB2 from Microsoft whereas Structured Query Language (SQL), pronounced "sequel", is a language that provides an interface to relational database systems. It was developed by IBM in the 1970s for use in System R. SQL is a de facto standard, as well as an ISO and ANSI standard.

SQL is used to perform various operations on RDBMS.

72.What is difference between Co-related sub query and nested sub query?

Correlated sub query runs once for each row selected by the outer query. It contains a reference to a value from the row selected by the outer query. Nested sub query runs only once for the entire nesting (outer) query. It does not contain any reference to the outer query row. For example,

Correlated Sub query:

select e1.empname, e1.basicsal, e1.deptno from emp e1 where e1.basicsal = (select max(basicsal) from emp e2 where e2.deptno = e1.deptno)

Nested Sub query:

select empname, basicsal, deptno from emp where (deptno, basicsal) in (select deptno, max(basicsal) from emp group by deptno)

73.WHAT OPERATOR PERFORMS PATTERN MATCHING?

Pattern matching operator is LIKE and it has to used with two attributes

1. % and

2. _ ( underscore )

% means matches zero or more characters and under score means mathing exactly one character

74)What is difference between Oracle and MS Access?

Oracle's features for distributed transactions, materialized views and replication are not available with MS Access. These features enable Oracle to efficiently store data for multinational companies across the globe. Also these features increase scalability of applications based on Oracle

75) What are disadvantages in Oracle and MS Access?

Oracle's features for distributed transactions, materialized views and replication are not available with MS Access. These features enable Oracle to efficiently store data for multinational companies across the globe. Also these features increase scalability of applications based on Oracle

76) What are features & advantages in Oracle and MS Access?

Oracle's features for distributed transactions, materialized views and replication are not available with MS Access. These features enable Oracle to efficiently store data for multinational companies across the globe. Also these features increase scalability of applications based on Oracle.

77.What is cluster. Cluster index and non cluster index ?

Clustered Index:- A Clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table may have only one clustered index. on-Clustered Index:- A Non-Clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows in the disk. The leaf nodes of a non-clustered index does not consists of the data pages. instead the leaf node contains index rows.

78.How can i hide a particular table name of our schema?

you can hide the table name by creating synonyms. e.g) you can create a synonym y for table x create synonym y for x;

79.What is difference between DBMS and RDBMS?

The main difference of DBMS & RDBMS is

RDBMS have Normalization. Normalization means to refining the redundant and maintain the stabilization.

the DBMS hasn't normalization concept.

80.What are the advantages and disadvantages of primary key and foreign key in SQL?

Primary key Advantages

1) It is a unique key on which all the other candidate keys are functionally dependent

Disadvantage

1) There can be more than one keys on which all the other attributes are dependent on.

Foreign Key Advantage

1)It allows referencing another table using the primary key for the other table