I’ve been doing a lot of sql queries on PrestoDB recently and just ran into Arrays. For one query I needed to see if an array was empty or not. To do that I needed to find the length of the array and see if it was greater than 0.
So my question - How do I get the length of an array in PrestoDB / PrestoSQL?
In order to get the length or size of an array in Presto, you can use the
cardinality takes in an array and will output the size or length of an array.
To solve my issue where I was looking for rows where the array field was non-empty, I could do something like this:
SELECT my_array FROM my_table WHERE CARDINALITY(my_array) > 0
Running this should give me all the rows in my table where
my_array is a non-empty array.
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