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how to find unique element in sql

DISTINCT
- select distinct * from employees; ==> 
           retrieves any row if it has at 
           least a single unique column.
- select distinct first_name from employees; ==> 
              retrieves unique names
              from table. (removes duplicates)
- select distinct count(*) from employees;
          retrieve number of unique rows
          if any row has at least a single unique data.

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what is a unique key in sql

1.Uniquely identifies a single row in the table.
2.Multiple values allowed per table.
3.Null values allowed.

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unique key in sql

Unique Key:
Only unique value and also can contain NULL

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how to find unique element in sql

what is a unique key in sql

unique key in sql

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