CODEWITHSUNDEEP
mysqlsqlselect
Jeggar Vance
Jeggar Vance

Reputation: 33

getting records of one and only one type

I was sitting several hours for trying to solve on specific problem but I couldn't get it. Finally, I decided to post it here. Here are some records,

╔════════╦════════════╦═════════╦══════════════════╗
║ AUTOID ║ PERSONNAME ║ FLOWER  ║ Other columns... ║
╠════════╬════════════╬═════════╬══════════════════╣
║      1 ║ Alex       ║ Rose    ║                  ║
║      2 ║ Rene       ║ Rose    ║                  ║
║      3 ║ Rene       ║ Jasmin  ║                  ║
║      4 ║ Darwin     ║ Rose    ║                  ║
║      5 ║ Alex       ║ Rose    ║                  ║
║      6 ║ Darwin     ║ Jasmin  ║                  ║
║      7 ║ Alex       ║ Rose    ║                  ║
║      8 ║ Rene       ║ Jasmin  ║                  ║
║      9 ║ Hello      ║ World   ║                  ║
║     10 ║ Hello      ║ World   ║                  ║
╚════════╩════════════╩═════════╩══════════════════╝

How can I get this result, the person who has only one type of flower on all his/her records.

╔════════════╦════════════╗
║ PERSONNAME ║ FLOWERNAME ║
╠════════════╬════════════╣
║ Alex       ║ Rose       ║
║ Hello      ║ World      ║
╚════════════╩════════════╝

the best one I tried was this query below, and still not working. 

SELECT  DISTINCT t1.PersonName, t1.Flower
FROM    TableName t1 
        INNER JOIN
        (
            SELECT  personname, COUNT(DISTINCT flower) totals
            FROM    tableName
            GROUP   BY personname, Flower
        )  t2 ON t1.personname = t2.personname and
                    t2.totals = 1

Any Idea?

Upvotes: 3

Views: 142

Answers (2)

Strawberry
Strawberry

Reputation: 33935

or, because there's always more than one way to skin a cat...

SELECT x.*
  FROM tablename x
  LEFT
  JOIN tablename y
    ON y.personname = x.personname
   AND ((y.flower <> x.flower)
    OR  (y.flower = x.flower AND y.autoid < x.autoid))
 WHERE y.autoid IS NULL;

Upvotes: 0

John Woo
John Woo

Reputation: 263933

you can use GROUP BY clause, HAVING clause and COUNT() on this problem, no need to join on a subquery

SELECT  PersonName, MAX(Flower) flowerName
FROM    TableName
GROUP   BY PersonName
HAVING  COUNT(DISTINCT Flower) = 1

Upvotes: 4

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