Multiple choice technology databases

What is the restriction on using UNION in embedded SQL ?

  1. It has to be in a CURSOR

  2. cannot be used in Embedded SQL

  3. No restrictions

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In embedded SQL (SQL embedded in host languages like C or Java), UNION operations that return multiple rows typically require a cursor context to properly fetch and process the result set. This is because UNION combines multiple result sets and the cursor provides a mechanism to iterate through the combined rows. Other isolation levels either use fewer locks or release locks earlier.

AI explanation

To answer this question, you need to understand the concept of embedded SQL and the usage of the UNION operator in embedded SQL.

Embedded SQL is a method of including SQL statements within a high-level programming language such as C or Java. It allows the programmer to combine the power and flexibility of SQL with the procedural capabilities of the programming language.

The UNION operator in SQL is used to combine the result sets of two or more SELECT statements into a single result set. It eliminates duplicate rows from the result set.

Now, let's go through each option to understand why it is correct or incorrect:

Option A) It has to be in a CURSOR - This option is the correct answer. When using the UNION operator in embedded SQL, it must be used within a CURSOR declaration. A CURSOR is a database object used to retrieve and manipulate data rows returned by a SQL query. It allows you to process the result set row by row. Therefore, the correct answer is A.

Option B) cannot be used in Embedded SQL - This option is incorrect. The UNION operator can be used in embedded SQL, but it must be used within a CURSOR declaration.

Option C) No restrictions - This option is incorrect. There are restrictions on using the UNION operator in embedded SQL, as mentioned in option A.

Option D) None of the above - This option is incorrect. The correct answer is A, as explained above.

Therefore, the correct answer is A) It has to be in a CURSOR. This option is correct because the UNION operator in embedded SQL must be used within a CURSOR declaration.

Keep practicing — related questions