3 Matching Annotations
- Jan 2023
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onlinelearning.berkeley.edu onlinelearning.berkeley.edu
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SUM(PURSE), COUNT(*) AS NUM_RACES
IMPORTANT!! : The group by clause is needed here because unlike in previous queries, we aren't simply taking a value in a prexisting table and adding it to a smaller table using the SELECT clause. We are using functions to create entirely new values. These values dont exist as part of the table, they kinda just float. Because these are floating unindexed values, the group by clause is needed to indicate how these new values should be presented in the output table for the query
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We used an inner join in the previous query, so non-matched rows are discarded
inner joins I think match two rows based on a common column
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However, when we place the JOIN keyword between the tables in the FROM clause, the predicate needs to be preceded by the ON keyword.
ON keyword needed before equivilancy statement when join keyword used
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