SQL (weight: 10%)

Consider the table below:

table A (
id integer primary key,
name varchar(20),
age integer
)

Write a query to return the list of unique names from table A

Question

SQL (weight: 10%)

Consider the table below:

table A (
  id  integer  primary key,
  name  varchar(20),
  age  integer
)
 
Write a  query to return the list of unique names from table A

Sigiloso · Accepted Answer

We cant use DISTINCT here. As the question asks for the Unique names to return, which means names that are not duplicated in the table,  we have to return the names that the count of that name in the table is 1.

SELECT name
FROM TableA t1
WHERE (

SELECT COUNT( name ) 
FROM TableA t2
WHERE t1.name = t2.name
) = 1;


                       id	name      age
			1	Test1	2
			2	Test2	0
			3	Test1	4
			4	Test3	5
			5	Test4	5
			6	Test2	5

In the above table you will get the result  Test3 and Test4 as those 2 are the only Unique names in the table. all the other names are duplicated.

Sigiloso · Answer

SELECT DISTINCT name
FROM  tableA

Garvit Jain · Answer

SELECT name FROM TableA GROUP BY name HAVING COUNT(name) = 1;

This will display only those names whose duplicates don't exist in the table.

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