To answer this question, we need to understand the concept of an IF-THEN-ELSE statement and compare it to the given functions.

An IF-THEN-ELSE statement is a control structure used in programming to make decisions based on certain conditions. It allows the program to execute different blocks of code depending on whether a specified condition is true or false.

Let's go through each option to determine which one is most similar in function to an IF-THEN-ELSE statement:

Option A) SQRT - This function calculates the square root of a given number. It does not involve any decision-making or conditional branching, so it is not similar to an IF-THEN-ELSE statement.

Option B) DECODE - This function is used to perform conditional branching within a SQL statement. It allows you to specify multiple conditions and their corresponding values. If the condition is true, it returns the specified value; otherwise, it returns a default value. This function closely resembles the functionality of an IF-THEN-ELSE statement, making it the correct answer.

Option C) NEW_TIME - This function is used to convert the time in one time zone to the time in another time zone. It does not involve any decision-making or conditional branching, so it is not similar to an IF-THEN-ELSE statement.

Option D) ROWIDTOCHAR - This function converts a ROWID value to a character string. It does not involve any decision-making or conditional branching, so it is not similar to an IF-THEN-ELSE statement.

Therefore, the correct answer is Option B) DECODE. This function can best be categorized as similar in function to an IF-THEN-ELSE statement because it allows for conditional branching within a SQL statement.

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To answer this question, let's analyze the given SQL statement:

SELECT (TO_CHAR(NVL(SQRT(59483), "INVALID")) FROM DUAL

This SQL statement is not valid. Here's why:

1. TO_CHAR() function: This function is used to convert a value to a character string. However, in this statement, it is being used on the result of another function or expression, which is missing.

2. NVL() function: This function is used to replace a null value with a specified value. In this statement, it is being used with the SQRT(59483) expression. However, the SQRT() function is not valid in this context.

3. SQRT() function: This function is used to calculate the square root of a number. However, in this statement, it is not being used correctly. It should be used with a valid numeric value, but the expression 59483 is not enclosed in single quotes.

4. "INVALID" string: In this statement, the string "INVALID" is used as a fallback value in case the SQRT() function returns null. However, the use of double quotes instead of single quotes for string literals is not valid in SQL.

Based on these observations, we can conclude that the given SQL statement is not valid (Option B is correct).

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To answer this question, you need to understand the purpose of the DEFINE_EDITOR parameter in SQL*Plus.

The DEFINE_EDITOR parameter in SQL*Plus is used to define the default text editor that SQL*Plus will use for editing commands or scripts. By default, SQL*Plus uses the operating system's default text editor.

Based on this information, let's go through each option to understand why it is correct or incorrect:

Option A) The emacs editor will become the SQL*Plus default text editor. This option is correct because issuing the DEFINE_EDITOR="emacs" command will set the emacs editor as the default text editor for SQL*Plus. This means that when you use the "EDIT" command in SQL*Plus, it will open the specified command or script in the emacs editor.

Option B) The emacs editor will start running immediately. This option is incorrect. Issuing the DEFINE_EDITOR="emacs" command does not start the emacs editor immediately. It only sets it as the default text editor for SQL*Plus.

Option C) The emacs editor will no longer be used by SQL*Plus as the default text editor. This option is incorrect. Issuing the DEFINE_EDITOR="emacs" command actually sets the emacs editor as the default text editor for SQL*Plus, so it will continue to be used as the default editor.

Option D) The emacs editor will be deleted from the system. This option is incorrect. Issuing the DEFINE_EDITOR="emacs" command does not delete the emacs editor from the system. It only sets it as the default text editor for SQL*Plus.

Therefore, the correct answer is: The emacs editor will become the SQL*Plus default text editor.

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To answer this question, you need to understand the scope of variables in SQL*Plus.

Option A) Until the database is shut down - This option is incorrect. Variables in SQL*Plus are not persistent and do not persist beyond the current session or statement. They are not retained when the database is shut down.

Option B) Until the instance is shut down - This option is incorrect. Similar to option A, variables in SQL*Plus are not persistent and do not persist beyond the current session or statement. They are not retained when the instance is shut down.

Option C) Until the statement completes - This option is correct. Variables in SQL*Plus are only valid for the duration of the current statement. Once the statement is completed, the variables are no longer available.

Option D) Until the session completes - This option is incorrect. Variables in SQL*Plus are only valid within the current session. Once the session is terminated, the variables are lost.

The correct answer is C) Until the statement completes. This option is correct because variables in SQL*Plus are only available for the duration of the current statement. Once the statement is completed, the variables are no longer accessible.

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