Informatics Practices
Assertion. There can be joins where all records from one of tables appear irrespective of their matching rows in the other table.
Reason. In LEFT JOIN, all rows from the left table appear in the result along with matching rows from the right table and NULL for the non-matching rows ; and same for the RIGHT JOIN where all rows came from the right table appear, along with only matching rows from the left table.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Answer
Both A and R are true and R is the correct explanation of A.
Explanation
In certain types of joins, such as LEFT JOIN and RIGHT JOIN, all records from one table appear in the result set regardless of whether they have matching rows in the other table. In a LEFT JOIN, all rows from the left table are included along with matching rows from the right table and NULL values for non-matching rows in the right table. Similarly, in a RIGHT JOIN, all rows from the right table are included along with matching rows from the left table and NULL values for non-matching rows in the left table.
Related Questions
Assertion. The join in which columns are compared for equality, is called an Equi-join.
Reason. The join condition can only compare columns with equal sign.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion. The join, in which columns are compared for equality, is called an Equi-join.
Reason. In non-equi joins, the columns are compared with non-equality conditional operators.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion. The UNION clause combines the rows of the participating tables, removing the duplicate rows.
Reason. To retain the duplicate rows in a UNION query, UNION ALL is used.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion. The MINUS and INTERSECT operators are similar.
Reason. The MINUS operator returns only the rows from the first result set while INTERSECT returns the common rows of both the result sets.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.