Discussion
To remove duplicate rows from the results of an SQL SELECT statement, the ________ qualifier specified must be included.
Answer: C
Correct answer: DISTINCT
SELECT DISTINCT removes duplicate rows from the result, comparing the whole selected row rather than any one column.
Note the cost: the engine must sort or hash the result to identify duplicates, so DISTINCT is not free on a large result set. It is also often a symptom rather than a fix - duplicates in a join usually mean the join condition is incomplete, and correcting that is better than filtering the result. UNIQUE is a constraint on a table, not a query qualifier.
No comment is present. Be the first to comment.
Loading…
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development