There is a table, MyTable(ID, Type, Date). Column 'Type' can have a value of 1 or 2.
Top 'x' rows, ordered by 'Date' and satisfying the following condition, have to be selected.('a' and 'b' are integer values)
The selected 'x' rows can contain only a maximum of 'a' Type 1 rows and 'b' Type 2 rows.(If a+b < x, then only a+b rows have to be selected.)
I might be completely wrong but I have an idea of doing this by having count() inside a WHERE clause. But I am not sure of how to do it.
How do I go about this problem?
UPDATE:
Example -
x = 5
Case 1:
a = 5, b = 5
Result: Rows 1,2,3,4,5
Case 2:
a = 4, b = 1
Result: Rows 1,2,4,6,8
Case 3:
a = 1, b = 5
Result: Rows 1,2,3,5,7
Case 4:
a = 2, b = 1
Result: Rows 1,2,4
You can do it by nesting a UNION inside another query:
select top #x *
from (
select top #a *
from table
where type = '1'
order by [date]
union
select top #b *
from table
where type = '2'
order by [date]
) t
order by [date]
Related
Consider the following table
id attribute
1 a
1 a
1 b
2 a
2 a
3 c
4 a
I want to select the ids that have attribute of 'a' only, ie 2 and 4.
Cant select 1 because 1 has 'a' and 'b', cant select 3 because it has 'c' only. We select 2 and 4 because it has 'a' value only.
You can use
SELECT id
FROM YourTable
GROUP BY id
HAVING MAX(attribute) = 'a' AND MIN(attribute) = 'a'
AND COUNT(*) = COUNT(attribute)
the
COUNT(*) = COUNT(attribute)
is to discard any id that have NULL attribute as well as a. Remove this if that is not the semantics you want or the column is not nullable anyway.
Please test this:
SELECT id
FROM attribute
GROUP BY id
HAVING
COUNT(DISTINCT attribute) = 1 AND MIN(attribute)= 'a';
I would like to write an Oracle query which returns a specific set of information. Using the table below, if given an id, it will return the id and value of B. Also, if B=T, it will return the next row as well. If that next row has a B=T, it will return that, and so on until a F is encountered.
So, given 3 it would just return one row: (3,F). Given 4 it would return 3 rows: ((4,T),(5,T),(6,F))
id B
1 F
2 F
3 F
4 T
5 T
6 F
7 T
8 F
Thank you in advance!
Use a sub-query to find out at what point you should stop, then return all row from your starting point to the calculated stop point.
SELECT
*
FROM
yourTable
WHERE
id >= 4
AND id <= (SELECT MIN(id) FROM yourTable WHERE b = 'F' AND id >= 4)
Note, this assumes that the last record is always an 'F'. You can deal with the last record being a 'T' using a COALESCE.
SELECT
*
FROM
yourTable
WHERE
id >= 4
AND id <= COALESCE(
(SELECT MIN(id) FROM yourTable WHERE b = 'F' AND id >= 4),
(SELECT MAX(id) FROM yourTable )
)
This is my example data (there are no indexes and I do not want to create any):
CREATE TABLE tblTest ( a INT , b INT );
INSERT INTO tblTest ( a, b ) VALUES
( 1 , 2 ),
( 5 , 1 ),
( 1 , 4 ),
( 3 , 2 )
I want the minimum value in of both column a and column b which is greater then a given value. E.g. if the given value is 3 then I want 4 to be returned.
This is my current solution:
SELECT MIN (subMin) FROM
(
SELECT MIN (a) as subMin FROM tblTest
WHERE a > 3 -- Returns 5
UNION
SELECT MIN (b) as subMin FROM tblTest
WHERE b > 3 -- Returns 4
)
This searches the table twice - once to get min(a) once to get min(b).
I believe it should be faster to do this with just one pass. Is this possible?
You want to use conditional aggregatino for this:
select min(case when a > 3 then a end) as minA,
min(case when b > 3 then b end) as minB
from tblTest;
To get the minimum of both values, you can use a SQLite extension, which handles multiple values for min():
select min(min(case when a > 3 then a end),
min(case when b > 3 then b end)
)
from tblTest
The only issue is that the min will return NULL if either argument is NULL. You can fix this by doing:
select coalesce(min(min(case when a > 3 then a end),
min(case when b > 3 then b end)
),
min(case when a > 3 then a end),
min(case when b > 3 then b end)
)
from tblTest
This version will return the minimum value, subject to your conditions. If one of the conditions has no rows, it will still return the minimum of the other value.
From the top of my head, you could modify the table and add a min value column to store the minimum value of the two columns. then query that column.
Or you can do this:
select min(val)
from
(
select min(col1, col2) as val
from table1
)
where
val > 3
The outer SELECT, queries the memory, not the table itself.
Check SQL Fiddle
I have data which is presented in multiple rows and columns with 0 or 1 values. What I'm trying to do is create a unique row for each 1, but there are sometimes multiple 1's in a row. For ex:
**A B C D**
1 0 1 1
0 0 0 1
1 1 0 0
I would like to have return six rows, all in one column like so
**RETURN**
A
C
D
D
A
B
Thanks in advance!
You can do this with a union all statement:
select val
from ((select 'A' as val from t where A = 1) union all
(select 'B' from t where B = 1) union all
(select 'C' from t where C = 1) union all
(select 'D' from t where D = 1)
) t
As a note: I hope you have other columns that you can include in the output. SQL tables are, by definition, not ordered. So, you really have no idea in your example of the original source for any given value.
I'm using Oracle 10g. I have a table with a number of fields of varying types. The fields contain observations that have been made by made about a particular thing on a particular date by a particular site.
So:
ItemID, Date, Observation1, Observation2, Observation3...
There are about 40 Observations in each record. The table structure cannot be changed at this point in time.
Unfortunately not all the Observations have been populated (either accidentally or because the site is incapable of making that recording). I need to combine all the records about a particular item into a single record in a query, making it as complete as possible.
A simple way to do this would be something like
SELECT
ItemID,
MAX(Date),
MAX(Observation1),
MAX(Observation2)
etc.
FROM
Table
GROUP BY
ItemID
But ideally I would like it to pick the most recent observation available, not the max/min value. I could do this by writing sub queries in the form
SELECT
ItemID,
ObservationX,
ROW_NUMBER() OVER (PARTITION BY ItemID ORDER BY Date DESC) ROWNUMBER
FROM
Table
WHERE
ObservationX IS NOT NULL
And joining all the ROWNUMBER 1s together for an ItemID but because of the number of fields this would require 40 subqueries.
My question is whether there's a more concise way of doing this that I'm missing.
Create the table and the sample date
SQL> create table observation(
2 item_id number,
3 dt date,
4 val1 number,
5 val2 number );
Table created.
SQL> insert into observation values( 1, date '2011-12-01', 1, null );
1 row created.
SQL> insert into observation values( 1, date '2011-12-02', null, 2 );
1 row created.
SQL> insert into observation values( 1, date '2011-12-03', 3, null );
1 row created.
SQL> insert into observation values( 2, date '2011-12-01', 4, null );
1 row created.
SQL> insert into observation values( 2, date '2011-12-02', 5, 6 );
1 row created.
And then use the KEEP clause on the MAX aggregate function with an ORDER BY that puts the rows with NULL observations at the end. whatever date you use in the ORDER BY needs to be earlier than the earliest real observation in the table.
SQL> ed
Wrote file afiedt.buf
1 select item_id,
2 max(val1) keep( dense_rank last
3 order by (case when val1 is not null
4 then dt
5 else date '1900-01-01'
6 end) ) val1,
7 max(val2) keep( dense_rank last
8 order by (case when val2 is not null
9 then dt
10 else date '1900-01-01'
11 end) ) val2
12 from observation
13* group by item_id
SQL> /
ITEM_ID VAL1 VAL2
---------- ---------- ----------
1 3 2
2 5 6
I suspect that there is a more elegant solution to ignore the NULL values than adding the CASE statement to the ORDER BY but the CASE gets the job done.
i dont know about commands in oracle but in sql you could use some how that
first use pivot table is contains consecutives numbers 0,1,2...
i'm not sure but in oracle the function "isnull" is "NVL"
select items.ItemId,
case p.i = 0 then observation1 else '' end as observation1,
case p.i = 0 then observation1 else '' end as observation2,
case p.i = 0 then observation1 else '' end as observation3,
...
case p.i = 39 then observation4 else '' as observation40
from (
select items.ItemId
from table as items
where items.item = _paramerter_for_retrive_only_one_item /* select one item o more item where you filter items here*/
group by items.ItemId) itemgroup
left join
(
select
items.ItemId,
p.i,
isnull( max ( case p.i = 0 then observation1 else '' end ), '' ) as observation1,
isnull( max ( case p.i = 1 then observation2 else '' end ), '' ) as observation2,
isnull( max ( case p.i = 2 then observation3 else '' end), '' ) as observation3,
...
isnull( max ( case p.i = 39 then observation4), '' ) as observation40,
from
(select i from pivot where id < 40 /*you number of columns of observations, that attach one index*/
)
as p
cross join table as items
lef join table as itemcombinations
on item.itemid = itemcombinations.itemid
where items.item = _paramerter_for_retrive_only_one_item /* select one item o more item where you filter items here*/
and (p.i = 0 and not itemcombinations.observation1 is null) /* column 1 */
and (p.i = 1 and not itemcombinations.observation2 is null) /* column 2 */
and (p.i = 2 and not itemcombinations.observation3 is null) /* column 3 */
....
and (p.i = 39 and not itemcombinations.observation3 is null) /* column 39 */
group by p.i, items.ItemId
) as itemsimplified
on itemsimplified.ItemId = itemgroup.itemId
group by itemgroup.itemId
About pivot table
create an pivot table, Take a look at that
pivot table schema
name: pivot columns: {i : datatype int}
How populate
create foo table
schema foo
name: foo column: value datatype varchar
insert into foo
values('0'),
values('1'),
values('2'),
values('3'),
values('4'),
values('5'),
values('6'),
values('7'),
values('8'),
values('9');
/* insert 100 values */
insert into pivot
select concat(a.value, a.value) /* mysql */
a.value + a.value /* sql server */
a.value | a.value /* Oracle im not sure about that sintax */
from foo a, foo b
/* insert 1000 values */
insert into pivot
select concat(a.value, b.value, c.value) /* mysql */
a.value + b.value + c.value /* sql server */
a.value | b.value | c.value /* Oracle im not sure about that sintax */
from foo a, foo b, foo c
the idea about pivot table can consult in "Transact-SQL Cookbook By Jonathan Gennick, Ales Spetic"
I have to admit that the above solution (by Justin Cave) is simpler and easier to understand but this is another good option
at the end like you said you solved