Teradata Teradata SQL 1 — Questions and Answers
Question 1: Which Teradata SQL clause is used to eliminate duplicate rows from a result set?
- DISTINCT (Correct answer)
- UNIQUE
- NODUPLICATE
- FILTER
Correct answer: DISTINCT
The DISTINCT keyword in a SELECT statement removes duplicate rows from the query result set.
Question 2: What does the QUALIFY clause do in Teradata SQL?
- Filters rows based on window function results (Correct answer)
- Defines table partitioning
- Applies row-level security
- Sets the query band
Correct answer: Filters rows based on window function results
QUALIFY filters rows based on the result of an ordered analytical (window) function, similar to HAVING for aggregates.
Question 3: Which Teradata join type returns all rows from both tables, including unmatched rows from each side?
- FULL OUTER JOIN (Correct answer)
- LEFT OUTER JOIN
- CROSS JOIN
- INNER JOIN
Correct answer: FULL OUTER JOIN
A FULL OUTER JOIN returns all rows from both tables, filling NULLs where there is no match on either side.
Question 4: In Teradata, what is the purpose of the SAMPLE clause?
- Returns a random subset of rows (Correct answer)
- Creates a table sample
- Copies statistics to another table
- Sets the row limit for exports
Correct answer: Returns a random subset of rows
The SAMPLE clause retrieves a random sample of rows from a table, useful for testing or statistical analysis.
Question 5: Which aggregate function in Teradata returns the middle value of an ordered dataset?
- MEDIAN (Correct answer)
- AVG
- MIDDLE
- CENTER
Correct answer: MEDIAN
The MEDIAN function returns the middle value of a numeric column when the values are sorted in ascending order.
Question 6: What does the CAST function do in Teradata SQL?
- Converts a value from one data type to another (Correct answer)
- Formats a string for display
- Joins two columns
- Creates a derived column alias
Correct answer: Converts a value from one data type to another
CAST converts an expression or column value from one data type to another, such as converting VARCHAR to INTEGER.
Teradata Teradata SQL 1
Which Teradata SQL clause is used to eliminate duplicate rows from a result set?