To answer this question, you need to understand the concept of cursors in SQL. Let's go through each option to understand why it is correct or incorrect:

Option A) Cursor is a named Private SQL area - This option is correct. A cursor is a named private SQL area that stores information about a specific SQL statement. It allows the database to process SQL statements and retrieve data in a controlled and efficient manner.

Option B) Cursor holds temporary results - This option is incorrect. Cursors do not hold temporary results. Instead, they hold the information needed to retrieve and process the results of a query.

Option C) Cursor is used for retrieving multiple rows - This option is correct. One of the main purposes of a cursor is to retrieve multiple rows of data from a result set. Cursors provide a way to fetch rows one by one or in batches, enabling the processing of large result sets.

Option D) SQL uses implicit Cursors to retrieve rows - This option is correct. SQL uses implicit cursors to retrieve rows. Implicit cursors are automatically created by the database management system (DBMS) when a SQL statement is executed. They are used to retrieve single rows or a small number of rows.

The correct answer is B) Cursor holds temporary results. This option is incorrect because cursors do not hold temporary results. Instead, they hold the information needed to retrieve and process the results of a query.

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To find the maximum salary paid in each job category of each department, we need to group the data by department and job category and then find the maximum salary within each group.

Let's go through each option to determine which one correctly achieves this:

Option A) SELECT dept_id, job_cat, MAX(salary) FROM employees WHERE salary > MAX(salary); This option is incorrect because the WHERE clause is comparing the salary to the maximum salary, which is not a valid comparison. Additionally, the MAX(salary) function cannot be used in the WHERE clause.

Option B) SELECT dept_id, job_cat, MAX(salary) FROM employees GROUP BY dept_id, job_cat; This option is correct because it uses the GROUP BY clause to group the data by department and job category. It then uses the MAX(salary) function to find the maximum salary within each group.

Option C) SELECT dept_id, job_cat, MAX(salary) FROM employees; This option is incorrect because it does not include the GROUP BY clause, which is necessary to group the data by department and job category.

Option D) SELECT dept_id, job_cat, MAX(salary) FROM employees GROUP BY dept_id; This option is incorrect because it only groups the data by department, but it does not include the job category in the grouping. We need to group by both department and job category to find the maximum salary in each job category of each department.

Therefore, the correct answer is Option B.

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

Option A) SUM(start_date) - This option is incorrect because the SUM function is used to calculate the sum of numeric values. The START_DATE column is of the DATE data type, which is not a numeric data type.

Option B) COUNT(start_date) - This option is correct. The COUNT function is used to count the number of rows in a column. It can be used on any data type, including the DATE data type.

Option C) AVG(start_date, end_date) - This option is incorrect because the AVG function is used to calculate the average of numeric values. It cannot be used with multiple columns.

Option D) MIN(start_date) - This option is correct. The MIN function is used to find the minimum value in a column. It can be used on the DATE data type.

Therefore, the two valid aggregate functions on the START_DATE column are COUNT(start_date) and MIN(start_date).

The correct answer is B,D.

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