Which of the following statements are TRUE about an SQL query?P : An S...
Statement P: An SQL query can contain a HAVING clause even if it does not have a GROUP BY clause
This statement is FALSE. The HAVING clause is used to filter the results of a GROUP BY query based on a condition. However, in order to use the HAVING clause, a GROUP BY clause is required. The GROUP BY clause is used to group the rows based on one or more columns, and then the HAVING clause can be used to filter the groups based on a condition.
Statement Q: An SQL query can contain a HAVING clause only if it has a GROUP BY clause
This statement is TRUE. As mentioned earlier, the HAVING clause is used in conjunction with the GROUP BY clause. It allows filtering of the grouped data based on a condition. Therefore, in order to use the HAVING clause, a GROUP BY clause must be present in the SQL query.
Statement R: All attributes used in the GROUP BY clause must appear in the SELECT clause
This statement is TRUE. When using the GROUP BY clause, all the attributes that are used for grouping must also appear in the SELECT clause. This ensures that the query returns the correct results by including the grouped attributes in the output. If an attribute used in the GROUP BY clause is not included in the SELECT clause, it will result in an error.
Statement S: Not all attributes used in the GROUP BY clause need to appear in the SELECT clause
This statement is FALSE. As mentioned in the previous statement, all attributes used in the GROUP BY clause must appear in the SELECT clause. This is to ensure that the grouped attributes are included in the output. If an attribute used in the GROUP BY clause is not included in the SELECT clause, it will result in an error.
Therefore, the correct statements are: