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.

Similar codes

1 vote164 views1 answer
Sql injection
SQL
14 votes167 views1 answer
Oracle new column
SQL
0 vote166 views1 answer
Sql select first and last record of each group
SQL
1 vote197 views2 answers
Duplicate key value violates unique constraint "django_admin_log_pkey"
SQL
0 vote177 views1 answer
Python mysql executemany
SQL
1 vote177 views2 answers
Sql server add time to date
SQL
1 vote183 views1 answer
What is int in mysql
SQL
20 votes169 views4 answers
Reset auto increment in MySQL
SQL
3 votes183 views2 answers
Wp do sql query from function
SQL
5 votes180 views3 answers
Oracle first day of last year
SQL