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Last tested: May 13, 2020

Explanation

The explore does some front-end operations that SQL Runner doesn't. For example, it tries to use the type defined in LookML to properly show the field values.

Solution

This is almost always because of a type mismatch. Often there is a string field on the database that has been given a type: number in LookML.

Remember that defining a type on a field doesn't do implicit casting. Try casting the sql parameter of your field to the datatype that you think the value should be. For example, sql: CAST(${TABLE}.id AS integer) ;;

This could also happen because of non-unique primary keys, which cause entries for non-unique values to show up as null on the explore page.