Explain normalization ?
Normalisation means refining the redundancy and maintain stablisation. there are four types of normalisation :
first normal forms, second normal forms, third normal forms and fourth Normal forms.
We cant create an Index on Index.. Index is stoed in user_index table.Every object that has been created on Schema is Schema Object like Table,View etc.If we want to share the particular data to various users we have to use the virtual table for the Base table...So tht is a view.
indexing is used for faster search or to retrieve data faster from various table. Schema containing set of tables, basically schema means logical separation of the database. View is crated for faster retrieval of data. It's customized virtual table. we can create a single view of multiple tables. Only the drawback is..view needs to be get refreshed for retrieving updated data.
Correlated subquery 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 subquery runs only once for the entire nesting (outer) query. It does not contain any reference to the outer query row.
For example,
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
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.Non-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.
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;
Normalisation means refining the redundancy and maintain stablisation. there are four types of normalisation :
first normal forms, second normal forms, third normal forms and fourth Normal forms.
We cant create an Index on Index.. Index is stoed in user_index table.Every object that has been created on Schema is Schema Object like Table,View etc.If we want to share the particular data to various users we have to use the virtual table for the Base table...So tht is a view.
indexing is used for faster search or to retrieve data faster from various table. Schema containing set of tables, basically schema means logical separation of the database. View is crated for faster retrieval of data. It's customized virtual table. we can create a single view of multiple tables. Only the drawback is..view needs to be get refreshed for retrieving updated data.
Correlated subquery 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 subquery runs only once for the entire nesting (outer) query. It does not contain any reference to the outer query row.
For example,
Correlated Subquery:
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 Subquery:
select empname, basicsal, deptno from emp where (deptno, basicsal) in (select deptno, max(basicsal) from emp group by deptno)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
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.Non-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.
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;
