I want to build query that will use parameter from query in subquery such as:
SELECT
A.Name,
CASE (SELECT SUM(A.Time) FROM A WHERE A.Name = A.Name)
FROM A
How can I do something like this. Thing needed mentioning is that the query will return multiple rows and for each of them I want to take sum based on the name from query.
You don't need a subquery here, use a windowed SUM:
SELECT A.[Name]
CASE SUM(A.[Time]) OVER (PARTITION BY A.[Name]) WHEN ... END AS Something --HOw do you SUM a "time"???
FROM A;
You can use analytical function for such requirements but if you want to know how to use subquery in select clause then you can use the alias as follows:
SELECT
A.Name,
(SELECT SUM(A.Time) FROM A WHERE t.Name = A.Name)
FROM A t -- t is the alias
Related
I am trying to find the count of obsv_dt which has less than million records
select obsv_dt,count(*) as c from table
group by obsv_dt
having c<1000000
order by c
is giving unable to resolve column 'c'. I get that 'c' is alias and this error is expected
How can i get this working?
select obsv_dt,count(*) as c from table
group by obsv_dt
having count(*) <1000000
order by count(*)
You cannot use the alias before it has been calculated; try:
select
obsv_dt,
count(obsv_dt) as c
from
table
group by obsv_dt
having count(obsv_dt) < 1000000
order by count(obsv_dt)
There is a subtle difference in using count(*) vs count(col). But often it does not matter. count(*) vs count(column-name) - which is more correct?
Below is the precedence of sql clauses:
FROM clause
ON clause
OUTER clause
WHERE clause
GROUP BY clause
HAVING clause
SELECT clause
DISTINCT clause
ORDER BY clause
TOP clause
Since HAVING clause is evaluated prior to the SELECT clause it is
unware of the aliases. Similarly for all clauses except for ORDER BY
where we can include the alias for sorting the result set.
I don't understand why I can't use this in my code :
SELECT MAX(SMTHNG), COUNT(MAX(SMTHNG))
FROM SomeTable;
Searched for an answer but didn't find it in documentation about these aggregate functions.
Also I get an SQL-compiler error "Invalid column name "SMTHNG"".
You want to know what the maximum SMTHNG in the table is with:
SELECT MAX(SMTHNG) FROM SomeTable;
This is an aggregation without GROUP BY and hence results in one single row containing the maximum SMTHNG.
Now you also want to know how often this SMTHNG occurs and you add COUNT(MAX(SMTHNG)). This, however, does not work, because you can not aggregate an aggregate directly.
This doesn't work either:
SELECT ANY_VALUE(max_smthng), COUNT(*)
FROM (SELECT MAX(smthng) AS max_smthng FROM sometable) t;
because the sub query only contains one row, so it's too late to count.
So, either use a sub query and select from the table again:
SELECT ANY_VALUE(smthng), COUNT(*)
FROM sometable
WHERE smthng = (SELECT MAX(smthng) FROM sometable);
Or count per SMTHNG before looking for the maximum. Here is how to get the counts:
SELECT smthng, COUNT(*)
FROM sometable
GROUP BY smthng;
And the easiest way to get the maximum from this result is:
SELECT TOP(1) smthng, COUNT(*)
FROM sometable
GROUP BY smthng
ORDER BY COUNT(*) DESC;
First of all, please read my comment.
Depending on what you're trying to achieve, the statement have to be changed.
If you want to count the highest values in SMTHNG field, you may try this:
SELECT T1.SMTHNG, COUNT(T1.SMTHNG)
FROM SomeTable T1 INNER JOIN
(
SELECT MAX(SMTHNG) AS A
FROM SomeTable
) T2 ON T1.SMTHNG = T2.A
GROUP BY T1.SMTHNG;
use cte like below or subquery
with cte as
(
select count(*) as cnt ,col from table_name
group by col
) select max(cnt) from cte
you can not use double aggregate function at a time on same column
I have a table like this:
Each keyword should have 4 pieces of data.
And I want to select the keywords that are less than 4 pieces of data.
I used select count(*) from mytable group by keyword to achieve something like this:
how can I select the keywords based on the count(*) result?
Here I want the keyword b from the result grid.
I am new to sql, thanks in advance.
to filter result by aggregation functions (like count) you need to use having, for example:
select keyword, count(*)
from mytable
group by keyword
having count(*) < 4
Just include having clause something like that :
select keyword
from mytable t
group by keyword
having count(*) < 4;
When I try to use the following SELECT statement:
SELECT [lots of columns]
FROM Client, Customer, Document, Group
WHERE [some conditions]
GROUP BY Group.id
SQL Server complains that the columns I selected are not part of the GROUP BY statement nor an aggregate function. Am I using GROUP BY wrong? What should I be using instead?
To return all single occurences of a group by field, together with associated field values, write a query like:
select group_field,
max(other_field1),
max(other_field2),
...
from mytable1
join mytable2 on ...
group by group_field
having count(*) = 1;
Yes, you are using GROUP BY incorrectly. The point of using GROUP BY is to use aggregate functions. If you have no aggregrate functions you probably want SELECT DISTINCT instead.
SELECT DISTINCT
col1,
col2,
-- etc
coln
FROM Client
JOIN Customer ON ...
JOIN Document ON ...
JOIN [Group] ON ...
WHERE ...
My first guess would be that the problem is that you have table called Group, which I believe is a reserved word in SQL. Try wrapping the Group name with ' '
You want to group by all columns you are selecting that is not in an aggregate funcion.
SELECT ProductName, ProductCategory, SUM(ProductAmount)
FROM Products
GROUP BY ProductName, ProductCategory
This will give you a disticnt result of Product names and categories with the sum total of product amount in all aggregate child records for that group.
SELECT A.ID, A.COLUMN_B, A.COLUMN_C FROM A
WHERE A.COLUMN_A IN
(
SELECT A.COLUMN_A
FROM B
INNER JOIN A ON B."COLUMN_A" = A."COLUMN_A"
WHERE B."COLUMN_B" = 'something'
UNION
SELECT A."COLUMN_A"
FROM A
WHERE A."COLUMN_D" IN (X,Y,Z) OR A."COLUMN_D" = 'something'
)
Now I want add a group by (A.ID) , and order by (A.COLUMN_B) DESC, and then select first to it. But DB won't allow. Any suggestions ? I can use LINQ to solve it once inner Union part is returned. But do now want to go that way.
There's a couple of things here.
First off - in DB2, when using GROUP BY, you can only select those columns listed in the grouping statement - everything else must be part of an aggregation function. So, grouping by a.Id and ordering by a.Column_B won't work - you'll need to order by SUM(a.Column_B) or something applicable.
Second... your query could use a bit of work in the general sense - specifically, you're self-joining twice, which you don't need to do at all. Try this instead:
SELECT a.Id, SUM(a.Column_B) as total, SUM(a.Column_C)
FROM a
WHERE a.Column_D in (X, Y, Z, 'Something')
OR EXISTS (SELECT '1'
FROM b
WHERE b.Column_A = a.Column_A
AND b.Column_B = 'Something')
GROUP BY a.Id
ORDER BY total DESC
FETCH FIRST 1 ROW ONLY
Swap out the SUM function for whatever is appropriate.
You can't use a column in the ORDER BY or SELECT that you haven't included in the GROUP BY, unless it's being aggregated (in a function like MAX() or COUNT() or SUM().
So, you could GROUP BY A.ID,A.COLUMN_B, and then ORDER BY COLUMN_B. Using a TOP 1 should work, too.
I just noticed that you're on DB2. I know that it will work this way on SQLServer. DB2 should be similar.
Worked the oterh way around. Just used Order By on A.ID and select row with max identity column.