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Alex Hort-Francis
12,924 PointsOn the `DISTINCT` keyword per column in the instructor's example query
I was a bit confused by this, due to his phrasing; my understanding is the DISTINCT keyword applies to all columns returned in the query, rather than per column, as I thought it sounded like he suggested.
For example, SELECT DISTINCT first_name, DISTINCT last_name would return a syntax error.
Whether or not a row is included while using the DISTINCT keyword would depend on which columns are included and therefore evaluated for 'distinct' values.
SELECT DISTINCT id, first_name, last_name would evaluate if any of the values in each row returned are distinct, which, given the use of the primary key id column, would return every row in the query, as every value for id (an incrementing number) should be distinct.
1 Answer
Steven Parker
231,269 PointsYou are quite right, and DISTINCT applies to all columns returned. So even without using the ID, a query with DISTINCT FIRST_NAME, LAST_NAME would indeed return all teachers even if two had the same first time.
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