- Can count individual attribute values COUNT(branch_name) COUNT(DISTINCT branch_name)
¨ Can also count the total number of tuples
COUNT(*)
🞑 If used with grouping, counts total number of tuples in each group
🞑 If used without grouping, counts total number of tuples
¨ Counting a specific attribute is useful when:
🞑 Need to count (possibly distinct) values of a particular attribute
🞑 Cases where some values in input multiset may be NULL
- As before, COUNT ignores NULL values (more on this next week)
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