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

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Question number: 249

» Database » MySQL

Short Answer Question▾

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

» Database » Oracle

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

Answer

b.

Explanation

Define placeholder column

Define Placeholder Column

Define placeholder column

  • 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.

    Following standard functions are provided by a summary column:

    • 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.