unique element in sql code example

Example 1: distinct keyword sql

Distinct: helps to displays the non duplicate
records when retrieving the records from a table.

SELECT DISTINCT FIRST_NAME FROM VISITORS;

Example 2: DISTINCT SQL

SELECT DISTINCT column1, column1, ..... FROM TABLE
/*DISTINCT WILL NOT SELECT THE SAME VALUES IN SAME COLUMN*/

Example 3: 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.

Example 4: unique key in sql

Unique Key:
Only unique value and also can contain NULL

Example 5: sql distinct

#List unique values in the df['name'] column
df.name.unique()