To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) SELECT SUBSTR ('Hello',) FROM dual; This option is incorrect because the SUBSTR function requires three arguments: the string, the starting position, and the length. In this case, the starting position and length are not provided.

Option B) SELECT INITCAP (TRIM ('Hello World',1,1) FROM dual; This option is incorrect because the TRIM function is used to remove specified characters from the beginning and/or end of a string. In this case, the starting position and length are not provided correctly.

Option C) SELECT LOWER (SUBSTR ('Hello World',1,1) FROM dual This option is incorrect because the SUBSTR function is used to extract a substring from a string. In this case, it is extracting the first character 'H' and converting it to lowercase using the LOWER function. It does not provide the desired result 'ello world'.

Option D) SELECT LOWER (SUBSTR ('Hello World',2,1) FROM dual; This option is incorrect because the SUBSTR function is used to extract a substring from a string. In this case, it is extracting the second character 'e' and converting it to lowercase using the LOWER function. It does not provide the desired result 'ello world'.

Option E) SELECT LOWER (TRIM ('H' FROM 'Hello World')) FROM dual; This option is correct because it uses the TRIM function to remove the letter 'H' from the string 'Hello World'. It then converts the remaining string 'ello world' to lowercase using the LOWER function. This provides the desired result 'ello world'.

The correct answer is Option E.

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• Wrong explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) INSTR returns the numeric position of a named character - This option is correct because the INSTR function in SQL returns the position of a specified character or substring within a string.

Option B) NVL2 returns the first non-null expression in the expression list - This option is incorrect because the NVL2 function in SQL returns the second expression if the first expression is not null, otherwise it returns the third expression.

Option C) DECODE translates an expression after comparing it to each search value - This option is correct because the DECODE function in SQL compares an expression to a list of search values and returns a result based on the matching value.

Option D) TRIM trims the heading or trailing characters (or both) from a character string - This option is correct because the TRIM function in SQL removes leading and/or trailing characters (or both) from a character string.

Option E) NVL compares two expressions and returns null if they are equal, or the first expression if they are not equal - This option is incorrect because the NVL function in SQL compares an expression to null and returns a specified value if the expression is null, otherwise it returns the expression itself.

Option F) NULLIF compares two expressions and returns null if they are equal, or the first expression if they are not equal - This option is correct because the NULLIF function in SQL compares two expressions and returns null if they are equal, otherwise it returns the first expression.

The correct answers are A, C, D, and F.

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• Wrong explanation

To answer this question, let's go through each option to understand which tasks can be performed using the TO_CHAR function:

Option A) Convert 10 to 'TEN' - The TO_CHAR function is used to convert a value to a character expression. It is not used to convert a numeric value to a string representation, so this option is incorrect.

Option B) Convert '10' to 10 - The TO_CHAR function is not used to convert a string representation of a number to a numeric value. This option is incorrect.

Option C) Convert '10' to '10' - The TO_CHAR function is used to convert a value to a character expression. In this case, it can be used to convert the string '10' to the string '10'. This option is correct.

Option D) Convert 'TEN' to 10 - The TO_CHAR function is not used to convert a string representation of a number to a numeric value. This option is incorrect.

Option E) Convert a date to a character expression - The TO_CHAR function can be used to convert a date to a character expression. This option is correct.

Option F) Convert a character expression to a date - The TO_CHAR function is used to convert a value to a character expression, not to convert a character expression to a date. This option is incorrect.

The correct answers are: C) Convert '10' to '10', and E) Convert a date to a character expression.

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• Wrong explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) The sort is in ascending order by default - This option is correct. If the ORDER BY clause does not specify ASC or DESC, the sort order is ascending by default.

Option B) The sort is in descending order by default - This option is incorrect. As mentioned above, the sort order is ascending by default.

Option C) The ORDER BY clause must precede the WHERE clause - This option is incorrect. The WHERE clause is used to filter rows based on a condition, and it comes before the ORDER BY clause in the SELECT statement.

Option D) The ORDER BY clause is executed on the client side - This option is incorrect. The ORDER BY clause is executed on the database server side, not on the client side.

Option E) The ORDER BY clause comes last in the SELECT statement - This option is correct. The ORDER BY clause is typically the last clause in a SELECT statement, used to sort the result set based on one or more columns.

Option F) The ORDER BY clause is executed first in the query execution - This option is incorrect. The ORDER BY clause is executed after the WHERE clause and other clauses (such as GROUP BY and HAVING) that may be present in the query.

The correct answers are A and E. The sort is in ascending order by default, and the ORDER BY clause comes last in the SELECT statement.

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• Wrong explanation

To answer this question, we need to understand what DML (Data Manipulation Language) statements are. DML statements are used to modify and manipulate data within a database.

Let's go through each option to determine if it is a DML statement:

Option A) COMMIT - This statement is not a DML statement. COMMIT is used to permanently save any changes made within a transaction.

Option B) MERGE - This statement is a DML statement. MERGE is used to combine data from two tables based on a specified condition.

Option C) UPDATE - This statement is a DML statement. UPDATE is used to modify existing data in a table.

Option D) DELETE - This statement is a DML statement. DELETE is used to remove data from a table.

Option E) CREATE - This statement is not a DML statement. CREATE is used to create new database objects, such as tables, indexes, or views.

Option F) DROP - This statement is not a DML statement. DROP is used to remove existing database objects.

Therefore, the correct answers are options B, C, and D.

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• Wrong explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) FROM - This option is incorrect because the FROM clause is used to specify the table or tables from which data will be retrieved.

Option B) SEARCH - This option is incorrect because there is no such SQL clause called SEARCH.

Option C) WHERE - This option is correct because the WHERE clause is used to specify a search condition to filter the rows returned by a SELECT statement.

Option D) WHILE - This option is incorrect because the WHILE clause is not used for specifying a search condition in SQL. It is typically used in programming languages like SQL Server's T-SQL to implement loops.

The correct answer is C) WHERE. This option is correct because the WHERE clause is used to specify a search condition in SQL.

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• Wrong explanation