Returns the unique not null value OR raise an exception

unique-agg

Returns the unique not null value OR raise an exception

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Case of use

When you need to normalize the content of an imported table, unique_agg checks the data while inserting in the new table.

For example you have imported_data tabla and want to extract info for countries and cities tables.

INSERT INTO countries (country_id, country_name)
  SELECT country_id, unique_agg(country_name)
    FROM imported_data
    GROUP BY country_id;

psql < bin/create_unique_agg.sql