How to find unique key 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.

Similar codes

1 vote307 views1 answer
Mysql list bigger table
SQL
5 votes316 views2 answers
Postgresql add not null constraint
SQL
2 votes265 views3 answers
Access denied for user 'root'@'localhost' mariadb
SQL
0 vote284 views1 answer
Sqlite update where exists
SQL
0 vote309 views1 answer
Sql convert unix time to date
SQL
0 vote288 views4 answers
Mysql select bottom 10 rows
SQL
0 vote278 views1 answer
Insert or update cassandra
SQL
-1 vote286 views3 answers
Update mongodb version ubuntu
SQL
1 vote293 views3 answers
Reset sql primary key
SQL
31 votes286 views3 answers
Sql count(*)
SQL