Question

I have a query in mysql

select f1,f2,f3 from tableName;

I want to remove duplicate value in field f1 and f2 only,

I have tired as follows

select f1,f2,f3 from tableName
group by f1,f2;

But it will remove duplicates in f1 only.Any body can suggest me that how to remove duplicates in f1 and f2.

topic_id    topic_name                    question_type
2237    Understanding Diversity           Comprehensive
2237    Understanding Diversity           Easy
2237    Understanding Diversity           Application
44315   Bhasha, boli, lipi, or Vayakaran  Intermediate

above is sample output having distinct value in question_type column only
here i want to remove duplicates from question_type and topic_id

expected output: having both topic_id and question_type distinct values

 44315  Bhasha, boli, lipi, or Vayakaran  Intermediate
 2237   Understanding Diversity           Comprehensive

Answer 1

My SQL really isn’t that great, but I think you need to do what is called a nested SELECT statement.

Here is the manual reference.

http://dev.mysql.com/doc/refman/5.0/en/subqueries.html

That would make the SQL look something like this.

SELECT f1,f2,f3 FROM (SELECT f1,f2,f3 FROM tableName AS table1 GROUP BY f1) AS table2 GROUP BY f2;

Note, that I had to use the AS to create an alias, else “tableName” would conflict with the parent SQL select.