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Q:

What are the difference between clustered and a non-clustered index?

Answer

- A clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table can have only one clustered index. The leaf nodes of a clustered index contain the data pages.


- 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 on disk. The leaf node of a non clustered index does not consist of the data pages. Instead, the leaf nodes contain index rows.

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Subject: SQL

Q:

What are defaults? Is there a column to which a default can’t be bound?

Answer

A default is a value which will be used by a column, if no value is supplied to that column while inserting data.


Yes, IDENTITY and TIMESTAMP columns are free from the bounds of default.

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Subject: SQL

Q:

State one similarity and difference between WHERE Clause and HAVING Clause?

Answer

Similarity: Both WHERE and HAVING Clause filters out records based on one or more conditions.


Difference: WHERE Clause can only be applied to a static non-aggregated column whereas HAVING is needed for aggregated columns.

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Subject: SQL

Q:

How can you generate debugging output from PL/SQL?

Answer

Use the DBMS_OUTPUT package. Another possible method is to use the SHOW ERROR command.

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Subject: SQL

Q:

How can you find a PL/SQL block, if the cursor is open?

Answer

By use of %ISOPEN status variable.


 

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Subject: SQL

Q:

What are PL/SQL cursor exceptions?

Answer

Cursor_Already_Open,  Invalid_Cursor.

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Subject: SQL

Q:

Name any three PL/SQL exceptions?

Answer

Too_many_rows.


No_Data_Found.


Zero_Error.


 

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Subject: SQL

Q:

Describe the use of PL/SQL table?

Answer

PL/SQL tables are scalar arrays that can be referenced by a binary digit. They can be used to store values for later queries and calculations.

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Subject: SQL