跨行的多列匹配

Question

I have a database and its structure looks like this:

1. The table is called Values
2. The columns of that table are: Key, Attribute, Value
3. An object is a series of rows that share the same Key .

For example:

ROWID   Key                                     Attribute   Value
*****   ************************************    *********   ***********************
1       9847CAD7-C430-4401-835B-A7FCE9A33A90    FirstName   Tito
2       9847CAD7-C430-4401-835B-A7FCE9A33A90    CreatedAt   2013-08-03 10:10:23:344
3       9847CAD7-C430-4401-835B-A7FCE9A33A90    UpdatedAt   2013-08-03 11:10:23:344
-----   ------------------------------------    ---------   -----------------------
4       4AE4B3F4-895B-4BF7-90E6-C889DA875D26    FirstName   Tito
5       4AE4B3F4-895B-4BF7-90E6-C889DA875D26    CreatedAt   2013-01-01 10:10:10:344
6       4AE4B3F4-895B-4BF7-90E6-C889DA875D26    UpdatedAt   2013-01-01 10:10:10:344

In the example above I have separated the two "objects" with a series of "-" to help understand how the data is structured.

The goal: select all rows where its UpdatedAt value is greater than its CreatedAt value and both share the same Key . In the above example, I'd like to match Key 9847CAD7-C430-4401-835B-A7FCE9A33A90 because its UpdatedAt value is greater than the value of CreatedAt (the matching should occur within the same "object".)

Any idea how I can accomplish this query? Thanks in advance for the help.

Answer 1

select 
t1.key
from
Table1 t1
inner join Table1 t2 on t1.key = t2.key 
where t1.Attribute = 'CreatedAt' and t2.Attribute = 'UpdatedAt'
and t1.value < t2.value

• see it working live in an sqlfiddle

Answer 2

Here's my version:

SELECT Key,
       MAX(CASE WHEN Attribute = 'FirstName' THEN Value END) As "First_Name",
       MAX(CASE WHEN Attribute = 'CreatedAt'  THEN Value END) As "Created_At",
       MAX(CASE WHEN Attribute = 'UpdatedAt'  THEN Value END) As "Updated_At"
FROM Value
GROUP BY Key
HAVING Created_At < Updated_At;

and SQL Fiddle

It shows all the attributes of the matching object .

Answer 3

Why does this feel like I am doing your homework ?

In any case it would be :

select o1.* from objects o1 
join objects o2 on o1.key = o2.key
where o1.attribute = "UpdatedAt"
and o2.attribute = "CreatedAt"
and o1.value > o2.value;

Which displays :

3    9847CAD7-C430-4401-835B-A7FCE9A33A90    UpdatedAt    2013-08-03 11:10:23

• Jeff Weiss