1
Q:

What is Log Shipping? 

Answer:



Q:

Count function in SQL returns the number of

A) groups B) values or rows
C) columns D) distinct values
 
Answer & Explanation Answer: B) values or rows

Explanation:

Count function in SQL returns the number of values or rows.

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1 220
Q:

The SQL keyword(s) ________ is used with wildcards.

A) LIKE only B) IN only
C) NOT IN only D) IN and NOT IN
 
Answer & Explanation Answer: A) LIKE only

Explanation:
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1 1084
Q:

A relational database developer refers to a record as

A) a relation B) an attribute
C) a criteria D) a tuple
 
Answer & Explanation Answer: D) a tuple

Explanation:

A relational database developer refers to a record as a tuple.

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0 603
Q:

What is an Extension of Entity Type?

Answer

The collections of entities of a particular Entity Type are grouped together into an entity set.

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0 268
Q:

How many joining conditions are required to join 4 tables in SQL?

A) 1 B) 2
C) 3 D) 4
 
Answer & Explanation Answer: C) 3

Explanation:

To join 'n' tables 'n-1' conditions should be satisfied.

So to join 4 tables 3 conditions should be satisfied.

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1 1027
Q:

Data integrity constraints are used to

A) Ensure that duplicate records are not entered into the table B) Prevent users from changing the values stored in the table
C) Control who is allowed access to the data D) Improve the quality of data entered for a specific property like table column
 
Answer & Explanation Answer: D) Improve the quality of data entered for a specific property like table column

Explanation:

Integrity constraints are used to ensure accuracy and consistency of data in a relational database. Data integrity is handled in a relational database through the concept of referential integrity. Many types of integrity constraints play a role in referential integrity (RI).

 

Hence, Data integrity constraints are used to Improve the quality of data entered for a specific property i.e, table column.

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0 280
Q:

Difference between Union and Union all?

Answer

The difference between Union and Union all is that Union all will not eliminate duplicate rows, instead it just pulls all rows from all tables fitting your query specifics and combines them into a table. A UNION statement effectively does a SELECT DISTINCT on the results set.

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Q:

A subquery in an sql select statement.

Answer

A Subquery or Inner query or a Nested query is a query within another SQL query and embedded within the WHERE clause.


Subqueries are most frequently used with the SELECT statement. The basic syntax is as follows::


SELECT column_name [, column_name ]
FROM table1 [, table2 ]
WHERE column_name OPERATOR
(SELECT column_name [, column_name ]
FROM table1 [, table2 ]
[WHERE])



A subquery is used to return data that will be used in the main query as a condition to further restrict the data to be retrieved.


Subqueries can be used with the SELECT, INSERT, UPDATE, and DELETE statements along with the operators like =, <, >, >=, <=, IN, BETWEEN, etc.


 


There are a few rules that subqueries must follow −


 


1. Subqueries must be enclosed within parentheses.


2. A subquery can have only one column in the SELECT clause, unless multiple columns are in the main query for the subquery to compare its selected columns.


3. An ORDER BY command cannot be used in a subquery, although the main query can use an ORDER BY. The GROUP BY command can be used to perform the same function as the ORDER BY in a subquery.


4. Subqueries that return more than one row can only be used with multiple value operators such as the IN operator.


5. The SELECT list cannot include any references to values that evaluate to a BLOB, ARRAY, CLOB, or NCLOB.


6. A subquery cannot be immediately enclosed in a set function.


7. The BETWEEN operator cannot be used with a subquery. However, the BETWEEN operator can be used within the subquery.

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