# 3i Infotech Papers: Sample Questions 249 - 250 of 1245

Examrace Placement Series prepares you for the toughest placement exams to top companies.

## Question number: 249

### Write in Short

What is the use of analysing the tables?

### Explanation

Use the ANALYZE statement to collect statistic, for example

• Collect or delete statistics about an index or index partition, table or table partition, index-organized table, cluster, or scalar object attribute.

• Validate the structure of an index or index partition, table or table partition, index-organized table, cluster, or object reference.

• Identify migrated and chained rows of a table or cluster.

## Question number: 250

MCQ▾

### Question

What are the types of calculated columns available?

### Choices

Choice (4) Response

a.

Procedure, Formula, & Placeholder columns

b.

Summary, Formula, & Placeholder columns

c.

Summary, Procedure, & Formula columns

d.

Summary, Placeholder, & Procedure column

b.

### Explanation

• Summary, Formula & Placeholder columns are the three types of calculated columns.

## Summary column:

• Used for calculating summary information like sum, average etc. on particular columns of a data group.

• Use a set of oracle aggregate functions.

• Datatypes of summary column depend on the data type of the source of the summary.

• Average

• Count

• First

• Last

• Maximum

• Minimum

• % of Total

• Sum

• Variance

## Formula column:

• Allows user-defined computation on the data from of one or more columns.

• Used to apply some custom logic on input data and return some value.

• Written using PL/SQL syntax and use PL/SQL function for computation on the data.

• Value can be character, number, or data and returned value match data type.

## Place holder column:

• An empty container at design time.

• Used to hold some value at runtime.

• Like local or global variables- used in the logic of a formula column or in report triggers.

• Value can be directly accessible in the report layout.