please answer these 3 questions thanks Answer Questions 12

please answer these 3 questions . thanks

Answer Questions 12 points each. ORDER BY PRODUCT P PRICE VENDOR CODE 33- is a schema? How many schemas can be used in one database? 34. What is a subquery? When is it used? Does the RDBMS deal with subqueries any differently from normal queries? 35. How can a table from database? Provide an example. be delete the

Solution

1)What is a schema ?How many schemas can be used in one database?

Ans)A schema is the logical structure of entities.A schema consists of many tables views,stored procedures etc.It shows the relationship between various tables.

If a user is created then oravle automatically create a schema and will be associate to that user.All his tables will be stored in that schema.

We can have more than one schema in a database.They will mention in the documentation related to the software product.

2)What is a subquery?When it is used? Dies the RDBMS deal will subqueries any differently from normal queries?

Ans)

A sub query is nothing but a query inside another query which is also called as nested queries.

Sub queries may found in select clause or may found in from clause or may found in where clause.

We will use subqueries when we know how to search for a value using select statement, but we don’t know the exact value.

The Subquery uuses select statement and will retrieve a group of values and those will be given as input to the outer query.

In case of subqueries First the sub query (or) inner query will be executed later the out query will be executed.

3)

We can use command to delete or drop a table from the database.

The syntax to drop table statement is

DROP TABLE TABLENAME;

Suppose we have am EMPLOYEE table in the database.If we want to drop that table ,then we have to use the statement

DROP TABLE EMPLOYEE;

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