Sampling Example 1: Unconditional Sampling, Single Sample Rate - Teradata Vantage

This example selects a sample of approximately 20% of the rows in the input table.

Input

The input table, score_category, categorizes the students (in the table students) by score in a given subject.

This statement creates score_category from students:

CREATE MULTISET TABLE score_category AS (
  SELECT *, CASE
    WHEN score <= 80 THEN 'fair'
    WHEN score > 80 AND score < 90 THEN 'very good'
    WHEN score >= 90 THEN 'excellent'
  END AS stratum FROM students
) WITH DATA;

SQL Call

SELECT * FROM Sampling (
  ON students PARTITION BY ANY
  USING
  SampleFraction (0.2)
  Seed (2)
) AS dt ORDER BY id;

Output