UNION combines compatible result sets and removes duplicates; UNION ALL keeps duplicates.
UNION combines compatible result sets and removes duplicates; UNION ALL keeps duplicates. Read the query line by line and identify the input table, the transformation, and the shape of the result before running it.
SELECT country AS value FROM customers WHERE country = 'India' UNION SELECT country AS value FROM customers WHERE country = 'UAE' ORDER BY value;
Before running the example, predict the output columns and whether the query returns one row, many rows, or possibly no rows.
In your own words, explain the main SQL feature in today’s lesson and why it answers the question.
Recall prompt: Both SELECTs must return the same number of columns. Close this page section mentally and explain the query from memory before proceeding.
Combine the distinct India and UAE country values into one result.
Both SELECTs must return the same number of columns.