Distinct group by deduplication

Select * From dc_restaurants; 31

Select distinct (restaurant_name), ID from dc_restaurants; 31 (deduplication will be performed based on the ID and specified ant_name)

 

Select distinct (restaurant_name), ID from dc_restaurants
Group by comment ant_name; 17

Select distinct ant_name, ID from dc_restaurants
Group by comment ant_name; 17

 

-- Deduplication based on a field: 1. Group by (do not pay attention to the field to be queried)
-- 2. distinct: Pay attention to the fields to be queried. If you want to query other non-deduplication fields,
-- The group by statement must be used to deduplicate fields. Otherwise, the group by statement is used to deduplicate multiple fields.

 

-- The group by group takes the record with the smallest ID by default ..
-- Distinct deduplication is distinguished by fields. * Indicates all fields. A single field refers
-- Remove duplicate data from the column.