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WITH yourTable AS (
SELECT 'john' AS first, 'Keats' AS last UNION ALL
SELECT 'Ray', 'Owano' UNION ALL
SELECT 'Keats', 'john' UNION ALL
SELECT 'Joseph', 'taylor' UNION ALL
SELECT 'Owano', 'Ray'
)
SELECT DISTINCT
CASE WHEN first < last THEN first ELSE last END AS first,
CASE WHEN first < last THEN last ELSE first END AS last
FROM yourTable;
| first | last |
|---|---|
| john | Keats |
| Joseph | taylor |
| Owano | Ray |