SQL Join Tables - sql

Question

Table one contains
ID|Name
1 Mary
2 John
Table two contains
ID|Color
1 Red
2 Blue
2 Green
2 Black
I want to end up with is
ID|Name|Red|Blue|Green|Black
1 Mary Y Y
2 John Y Y Y
Thanks for any help.
Thanks for the responses. I'm going to re-post this with some additional info about exactly what I'm trying to do that may complicate this. Can someone close this?

Answer 1

If you use T-SQL you can use PIVOT (http://msdn.microsoft.com/en-us/library/ms177410.aspx)
Here is query I used:
declare #tbl_names table(id int, name varchar(100))
declare #tbl_colors table(id int, color varchar(100))
insert into #tbl_names
select 1, 'Mary'
union
select 2, 'John'
insert into #tbl_colors
select 1, 'Red'
union
select 1, 'Blue'
union
select 2, 'Green'
union
select 2, 'Blue'
union
select 2, 'Black'
select name,
case when [Red] is not null then 'Y' else '' end as Red,
case when [Blue] is not null then 'Y' else '' end as Blue,
case when [Green] is not null then 'Y' else '' end as Green,
case when [Black] is not null then 'Y' else '' end as Black
from
(
select n.id, name, color from #tbl_names n
inner join #tbl_colors c on n.id = c.id
) as subq
pivot
(
min(id)
FOR color IN ([Red], [Blue], [Green], [Black])
) as pvt
And here is output:
John Y Y Y
Mary Y Y

Answer 2

I can use a CASE statement with a subquery to input the Y values.
select ID, Name,
case
when exists (select * from Colors C where C.ID = N.ID and Color = 'Red') then
'Y'
else
NULL
end
,
case
when exists (select * from Colors C where C.ID = N.ID and Color = 'Blue') then
'Y'
else
NULL
end
,
case
when exists (select * from Colors C where C.ID = N.ID and Color = 'Green') then
'Y'
else
NULL
end
,
case
when exists (select * from Colors C where C.ID = N.ID and Color = 'Black') then
'Y'
else
NULL
end
from Names N

Answer 3

I think you're going to have to end up with something like this :
SELECT t1.ID,
t1.Name,
CASE
WHEN red.ID IS NULL THEN ''
ELSE 'Y'
END As Red,
CASE
WHEN blue.ID IS NULL THEN ''
ELSE 'Y'
END As Blue
FROM Table1 t1
LEFT JOIN Table2 Red
ON t1.ID = Red.ID AND Red.Color = 'Red'
LEFT JOIN Table2 Blue
ON t1.ID = Blue.ID AND Blue.Color = 'Blue'
MS Sql does not support PIVOT queries like MS Access.

Answer 4

As other commenters have pointed out, you don't display exactly how you are linking people and colors. If you are using a linking table (person_id, color_id) then there is no way to solve this problem in standard SQL since it requires a pivot or cross-tabulation, which is not part of standard SQL.
If you are willing to add the condition that the number of colors is limited and known and design time, you could come up with a solution using one join for each color and CASE or IF functions in the SQL. But that would not be elegant and, furthermore, I wouldn't trust that condition to stay true for very long.
If you are able to come up with a different way of storing the color linking information you might have more options for producing the output you want, but a different storage technique implies some degree of denormalization of the database which could well cause other difficulties.
Otherwise, you will have to do this in a stored procedure or application code.

Answer 5

Contrary to what some other posters have said; I see no need for a third table. If colors are a well known enumeration in you application then you don't need a "Color" table.
What you are looking for is a PIVOT like this one.