Can a MySQL query turn rows into columns? - mysql

Question

I have a number of tables I am trying to combine with joins but as such, the results are returned in a number of rows whereas I would like to have them generated as new columns.
member_information Table
MemberID | FirstName | LastName
---------------------------------
1 | John | Harris
2 | Sarah | Thompson
3 | Zack | Lewis
member_dependent_information Table
MemberID | FirstName | LastName | Type
---------------------------------------
1 | Amy | Harris | 1
2 | Bryan | Thompson | 1
2 | Dewey | Thompson | 2
2 | Tom | Thompson | 2
3 | Harry | Lewis | 2
3 | Minka | Lewis | 1
MySQL Query:
SELECT
t1.FirstName,
t1.LastName,
t1.MemberID,
IF(t2.Type = '1',CONCAT(t2.FirstName,' ',t2.LastName),'') AS Spouse_Name,
IF(t2.Type = '2',CONCAT(t2.FirstName,' ',t2.LastName),'') AS Child_Name,
FROM
member_dependent_information t2
INNER JOIN
member_information t1
USING
(MemberID)
ORDER BY
t1.LastName ASC,
t1.MemberID ASC;
Ideal Results
MemberID | FirstName | LastName | Spouse_Name | Child_Name1 | Child_Name2
--------------------------------------------------------------------------------
1 | John | Harris | Amy Harris | NULL | NULL
2 | Sarah | Thompson | Bryan Thompson | Dewey Thompson | Tom Thompson
3 | Zack | Lewis | Mika Lewis | Harry Lewis | NULL
ACTUAL RESULTS
MemberID | FirstName | LastName | Spouse_Name | Child_Name
-------------------------------------------------------------------
1 | John | Harris | Amy Harris | NULL
2 | Sarah | Thompson | Bryan Thompson | NULL
2 | Sarah | Thompson | NULL | Dewey Thompson
2 | Sarah | Thompson | NULL | Tom Thompson
3 | Zack | Lewis | Mika Lewis | NULL
3 | Zack | Lewis | NULL | Harry Lewis
While my query returns the "correct" data in multiple rows, it does not combine the result into one single row as needed.
The suggestion for Pivot Tables / Crosstabs has been mentioned below but every reference I am able to find suggests using mathematic calculations or that the number of fields to be returned is known. I will not know this information as a single member COULD have up to 100 dependents (although more like 4-8)
UPDATE #1
I feel I am getting closer to the final solution. I added the function GROUP_CONCAT to my query which returns ALL firstnames in a single column and ALL last names in a single column but still need to break them out into their own individual columns.
New function is:
SELECT
t1.MemberID,
t1.FirstName,
t1.LastName,
GROUP_CONCAT(t2.FirstName) AS Dep_Firstnames,
GROUP_CONCAT(t2.LastName) AS Dep_LastNames
FROM
member_information t1
LEFT OUTER JOIN member_dependent_information t2
ON t1.MemberID = t2.MemberID
WHERE
t1.Status = 1
GROUP BY
t1.MemberID

Answer 1

Sometimes the first step to solving your problem is knowing what it's called. After that, it's simply a matter of googling. What you are trying to create is called a pivot table or crosstab report. Here is a link explaining how to create pivot tables in MySQL. And here is a more in depth tutorial.
UPDATE:
Now that you've updated the question, I have a clearer idea of what you are trying to accomplish. I'll give you an alternative solution which is similar but not exactly what you want based on MySQL's GROUP_CONCAT function.
select t1.FirstName, t1.LastName, group_concat(concat(t2.FirstName, ' ', t2.LastName))
from member_information as t1
left outer join member_dependent_information as t2 on t2.MemberID=t1.MemberID
group by t1.MemberID;
I've verified this query as follows. First the setup:
create table member_information (
MemberID int unsigned auto_increment primary key,
FirstName varchar(32) not null,
LastName varchar(32) not null
) engine=innodb;
create table member_dependent_information (
MemberID int unsigned not null,
FirstName varchar(32) not null,
LastName varchar(32) not null,
Type int unsigned not null,
foreign key (MemberID) references member_information(MemberID)
) engine=innodb;
insert into member_information (MemberID, FirstName, LastName) values
(1, 'John', 'Harris'),
(2, 'Sarah', 'Thompson'),
(3, 'Zack', 'Lewis');
insert into member_dependent_information (MemberID, FirstName, LastName, `Type`) values
(1, 'Amy', 'Harris', 1),
(2, 'Bryan', 'Thompson', 1),
(2, 'Dewey', 'Thompson', 2),
(2, 'Tom', 'Thompson', 2),
(3, 'Harry', 'Lewis', 2),
(3, 'Minka', 'Lewis', 1);
And now the query and results:
mysql> select t1.FirstName, t1.LastName, group_concat(concat(t2.FirstName, ' ', t2.LastName))from member_information as t1
-> left outer join member_dependent_information as t2 on t2.MemberID=t1.MemberID
-> group by t1.MemberID;
+-----------+----------+------------------------------------------------------+
| FirstName | LastName | group_concat(concat(t2.FirstName, ' ', t2.LastName)) |
+-----------+----------+------------------------------------------------------+
| John | Harris | Amy Harris |
| Sarah | Thompson | Bryan Thompson,Dewey Thompson,Tom Thompson |
| Zack | Lewis | Harry Lewis,Minka Lewis |
+-----------+----------+------------------------------------------------------+
3 rows in set (0.00 sec)

Answer 2

I'm not sure how the OP transformed from having programID and Status to how it is now, but the closest thing I would be able to get is (which does not require pivot tables):
SELECT t1.MemberID,
t1.FirstName,
t1.LastName,
concat(t2.FirstName, ' ', t2.LastName) as Spouse_Name,
group_concat(concat(t3.FirstName, ' ', t3.LastName) ORDER BY t3.FirstName) as Children_names
FROM member_information t1
LEFT JOIN member_dependent_information t2 ON (t1.MemberID=t2.MemberID AND t2.Type=1)
LEFT JOIN member_dependent_information t3 ON (t1.MemberID=t3.MemberID and t3.Type=2)
GROUP BY MemberID;
Which produces:
+----------+-----------+----------+----------------+-----------------------------+
| MemberID | FirstName | LastName | Spouse_Name | Children_names |
+----------+-----------+----------+----------------+-----------------------------+
| 1 | John | Harris | Amy Harris | NULL |
| 2 | Sarah | Thompson | Bryan Thompson | Dewey Thompson,Tom Thompson |
| 3 | Zack | Lewis | Minka Lewis | Harry Lewis |
+----------+-----------+----------+----------------+-----------------------------+
and it would be "easy" with any programming language to extract that Children_names into separate columns.

Answer 3

This is not exactly what you are looking for, but it might be a step in the right direction.
SELECT
Table1.memberIDs,
Table1.firstname,
Table1.lastnames,
Table2.programIDs,
Table3.description
FROM
Table1,
Table2,
Table3
WHERE
Table1.memberIDs = Table2.memberIDs AND
Table2.programIDs = Table3.programID