Optimizing single-table queries
Consider all possible plans
Covering indexes
- The query restricts columns a and b
- And projects only column c.
- If we have an index keyed by either (a, b, c) or (b, a, c),
then we can use the covering index optimization.
- Use the index to find rows satisfying a = 1 and b = 10.
- Then instead of retrieving rows from the heap to obtain c,
just get it from the index.
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