I'm a bit stuck on this supposedly basic SQL and would appreciate some pointers.
I'd like to get a single row result from combining multiple sub-selects. What I have so far (which of course does not work):
select * from (
(select count(*) from a where name='a') as a),
(select count(*) from b where name='d') as b)
) as foo;
...and I'm looking for a result along the lines of:
a | b
-----
1 | 2
Given the source tables:
Table a:
id | name
----+------
1 | a
2 | b
3 | c
Table b:
id | name
----+------
1 | a
2 | b
3 | c
4 | d
5 | d
I also tried something along the lines of
select count(a.*), count(b.*) from a, b where a.name='a' and b.name='d';
which produces:
count | count
------+-------
2 | 2
I'd appreciate any assistance.
thanks
Just use:
select (select count(*) from a where name='a') as a,
(select count(*) from b where name='d') as b
Related
Suppose I have a table like this :
Column A | Column B
---------+---------
1 | A
1 | B
2 | A
2 | A
2 | C
3 | A
3 | A
3 | B
3 | B
I want to write a query that groups the values in such a way that i get a table like this :
Column A | Column B
---------+---------
1 | A
1 | B
2 | A
2 | C
3 | A
3 | B
You are looking for DISTINCT. DISTINCT removes duplicates from your query result.
select distinct * from mytable;
An alternative would be aggregation. You'd get a result row per a and b by grouping by them. You'd only use this however, when you want aggregates, e.g. the number of rows, a sum, an average, etc., because otherwise you can use DISTINCT as shown and should prefer it.
select a, b, count(*) from mytable group by a, b;
You need to use GROUP BY on both column.
select col1, col2 from test group by col1,col2;
See SQLFIDDLE
I know questions regarding this error message have been asked already, but I couldn't find any that really fit my problem.
I have a table with three columns (A,B,C) containing different values and I need to identify all the identical combination. For example out of "TABLE A" below:
| A | B | C |
| 1 | 2 | 3 |
| 1 | 3 | 3 |
| 1 | 2 | 3 |
| 2 | 2 | 2 |
| 1 | 3 | 3 |
... I would like too get "TABLE B" below:
| A | B | C | count |
| 1 | 2 | 3 | 1 |
| 1 | 3 | 3 | 1 |
| 2 | 2 | 2 | 1 |
(I need the last column "count" with 1 in each row for later usage)
When I try with "group by A,B,C" I get the error mentioned in the title. Any help would be greatly appreciated!
FYI, I don't think it really changes the matter, but "TABLE A" is obtained from an other table: "SOURCE_TABLE", thanks to a query of the type:
select (case when ... ),(case when ...),(case when ...) from SOURCE_TABLE
and I need to build "TABLE B" with only one query.
i think what you are after of is using distinct
select distinct A,B,C, 1 [count] -- where 1 is a static value for later use
from (select ... from sourcetable) X
Sounds like you have the right idea. My guess is that the error is occurring due to an outer reference in your CASE statements. If you wrapped your first query in another query, it may alleviate this issue. Try:
SELECT A, B, C, COUNT(*) AS [UniqueRowCount]
FROM (
SELECT (case when ... ) AS A, (case when ...) AS B, (case when ...) AS C FROM SOURCE_TABLE
) AS Subquery
GROUP BY A, B, C
After re-reading your question, it seems that you're not counting at all, just putting a "1" after each distinct row. If that's the case, then you can try:
SELECT DISTINCT A, B, C, [Count]
FROM (
SELECT (case when ... ) AS A, (case when ...) AS B, (case when ...) AS C, 1 AS [Count] FROM SOURCE_TABLE
) AS Subquery
Assuming your outer reference exceptions were occurring in only your aggregations, you should also simply try:
SELECT DISTINCT (case when ... ) AS A, (case when ...) AS B, (case when ...) AS C, 1 AS [Count] FROM SOURCE_TABLE
Hi i have a situation here with Oracle SQL to come out with the sql result as the following :-
Company No of Employees Group Derived Field
a 1 x
b 1 x
c 2 y
d 1 y
so based on the group if all the company has same no of employees then i want the derived field to be
true else false.
So for group x , if company a and b has the same no of employees then derived field for
a and b would be true. As for c and d because the no of employees is different so the derived field
should be false.
any help would be appreciated. thanks
You want to use an analytic function. I think this is what you want:
select t.*,
(case when min(NumEmployees) over (partition by grp) =
max(NumEmployees) over (partition by grp)
then 1
else 0
end) as DerivedField
from table t;
Note: I usually represent booleans as 0 and 1.
Here is a purely sql solution. Assume the column names are company,number,ggroup,test.
for convenience create a view of table t as
create view gnums as select count(distinct number)as gnum,count(number) as num, ggroup from t group by ggroup;
The this select
select a.*,b.gnum = 1 and b.num <> 1 as test from t a,gnums b where a.ggroup = b.ggroup;
yields
id | company | number | ggroup | test
----+---------+--------+--------+------
1 | a | 1 | x | t
2 | b | 1 | x | t
3 | c | 2 | y | f
4 | d | 1 | y | f
5 | e | 2 | z | f
I added row e to show that any group with only one company should yield false, assuming that's what you intended.
I am trying to select several columns from a table where one of the columns is unique. The select statement looks something like this:
select a, distinct b, c, d
from mytable
The table looks something like this:
| a | b | c | d | e |...
|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5
| 1 | 2 | 3 | 4 | 6
| 2 | 5 | 7 | 1 | 9
| 7 | 3 | 8 | 6 | 4
| 7 | 3 | 8 | 6 | 7
So the query should return something like this:
| a | b | c | d |
|---|---|---|---|
| 1 | 2 | 3 | 4
| 2 | 5 | 7 | 1
| 7 | 3 | 8 | 6
I just want to remove all of the rows where b is duplicated.
EDIT: There seems to be some confusion about which row I want to be selected in the case of duplicate b values. I don't care because the a, c, and d should (but are not guaranteed to) be the same.
Try this
SELECT * FROM (SELECT ROW_NUMBER() OVER (PARTITION BY b ORDER BY a) NO
,* FROM TableName) AS T1 WHERE NO = 1
I think you are nearly there with DISTINCT try:
SELECT DISTINCT a, b, c, d
FROM myTable
You haven't said how to pick a row for each b value, but this will pick one for each.
Select
a,
b,
c,
d,
e
From (
Select
a,
b,
c,
d,
e,
row_number() over (partition by b order by b) rn
From
mytable
) x
Where
x.rn = 1
If you don't care what values you get for B, C, D, and E, as long as they're appropriate for that key, you can group by A:
SELECT A, MIN(B), MIN(C), MIN(D), MIN(E)
FROM MyTable
GROUP BY A
Note that MAX() would be just as valid. Some RDBMSs support a FIRST() aggregate, or similar, for exactly these circumstances where you don't care which value you get (from a certain population).
This will return what you're looking for but I think your example is flawed because you've no determinism over which value from the e column is returned.
Create Table A1 (a int, b int, c int, d int, e int)
INSERT INTO A1 (a,b,c,d,e) VALUES (1,2,3,4,5)
INSERT INTO A1 (a,b,c,d,e) VALUES (1,2,3,4,6)
INSERT INTO A1 (a,b,c,d,e) VALUES (2,5,7,1,9)
INSERT INTO A1 (a,b,c,d,e) VALUES (7,3,8,6,4)
INSERT INTO A1 (a,b,c,d,e) VALUES (7,3,8,6,7)
SELECT * FROM A1
SELECT a,b,c,d
FROM
(
SELECT ROW_NUMBER() OVER (PARTITION BY b ORDER BY a) RowNum ,*
FROM A1
) As InnerQuery WHERE RowNum = 1
You cannot put DISTINCT on a single column. You should put it right after the SELECT:
SELECT DISTINCT a, b, c, d
FROM mytable
It return the result you need for your sample table. However if you require to remove duplicates only from a single column (which is not possible) you probably misunderstood something. Give us more descriptions and sample, and we try to guide you to the right direction.
I have a table similar to:-
+----+---+---+
| Id | A | B |
+----+---+---+
| 1 | 1 | 2 |
+----+---+---+
| 2 | 2 | 1 |
+----+---+---+
| 3 | 3 | 4 |
+----+---+---+
| 4 | 0 | 5 |
+----+---+---+
| 5 | 5 | 0 |
+----+---+---+
I want to remove all duplicate pairs of values, regardless of which column contains which value, e.g. after whatever the query might be I want to see:-
+----+---+---+
| Id | A | B |
+----+---+---+
| 1 | 1 | 2 |
+----+---+---+
| 3 | 3 | 4 |
+----+---+---+
| 4 | 0 | 5 |
+----+---+---+
I'd like to find a solution in Microsoft SQL Server (has to work in <= 2005, though I'd be interested in any solutions which rely upon >= 2008 features regardless).
In addition, note that A and B are going to be in the range 1-100 (but that's not guaranteed forever. They are surrogate seeded integer foreign keys, however the foreign table might grow to a couple hundred rows max).
I'm wondering whether I'm missing some obvious solution here. The ones which have occurred all seem rather overwrought, though I do think they'd probably work, e.g.:-
Have a subquery return a bitfield with each bit corresponding to one of the ids and use this value to remove duplicates.
Somehow, pivot, remove duplicates, then unpivot. Likely to be tricky.
Thanks in advance!
Test data and sample below.
Basically, we do a self join with an OR criteria so either a=a and b=b OR a=b and b=a.
The WHERE in the subquery gives you the max for each pair to eliminate.
I think this should work for triplicates as well (note I added a 6th row).
DECLARE #t table(id int, a int, b int)
INSERT INTO #t
VALUES
(1,1,2),
(2,2,1),
(3,3,4),
(4,0,5),
(5,5,0),
(6,5,0)
SELECT *
FROM #t
WHERE id NOT IN (
SELECT a.id
FROM #t a
INNER JOIN #t b
ON (a.a=b.a
AND a.b=b.b)
OR
(a.b=b.a
AND a.a = b.b)
WHERE a.id > b.id)
Try:
select min(Id) Id, A, B
from (select Id, A, B from DuplicatesTable where A <= B
union all
select Id, B A, A B from DuplicatesTable where A > B) v
group by A, B
order by 1
Not 100% tested and I'm sure it can be tidied up but it produces your required result:
DECLARE #T TABLE (id INT IDENTITY(1,1), A INT, B INT)
INSERT INTO #T
VALUES (1,2), (2,1), (3,4), (0,5), (5,0);
SELECT *
FROM #T
WHERE id IN (SELECT DISTINCT MIN(id)
FROM (SELECT id, a, b
FROM #T
UNION ALL
SELECT id, b, a
FROM #T) z
GROUP BY a, b)