I have the following table in Postgresql. The first 4 records are the base data and the others were generated with the ROLLUP function.
I want to add a column "grp_1" that will display the first non-null value of the columns grp1_l1, grp2_l2 and grp2_l3
I can get to the desired result by nesting 3 "case" functions using the SQL below, but my real table has 4 groups with each 8 to 10 columns (so a lot of nested "case" function).
sql:
SELECT grp1_l1, grp1_l2, grp1_l3, case when grp1_l1 is not null then grp1_l1 else case when grp1_l2 is not null then grp1_l2 else case when grp1_l3 is not null then grp1_l3 else null end end end as grp1, value
FROM public.query_test;
Is there a better and more scalable to handle this requirement ? Any suggestions are welcome.
The id will not always have 3 digits, that is just the case in my example here
Use coalesce() it's defined as "returns the first of its arguments that is not null" - which is exactly what you want.
coalesce(grp1_l1, grp1_l2, grp1_l3)
Related
Given a table of random numbers as follows:
** Person table schema **
Name
Marks1
Marks2
I want to return a table with similar structure and headings, where if the sum of a column is odd, the column shows the maximum value for that column, and when the sum is even, it shows the minimum value by using a case statement.
** output table schema **
Marks1
Marks2
I've tried the following code.
select Marks1,Marks2 ,
(case
when mod(sum(Marks1),2)=0 then
min(Marks1)
else max(Marks1)
end) as Marks1 ,
(case
when mod(sum(Marks2),2)=0 then
min(Marks2)
else max(Marks2)
end) as Marks2
from numbers
group by Marks1;
Sample output -
TABLE
Ash 56 45
David 45 35
Output -
56 35
As 56+45 = 101 odd number so output 56(max number). Whereas in marks2 column, 45+35 =80, even number so output 35(min number).
Can anyone tell me what's wrong with it? Thanks in advance.
Use a CTE to get your min(), max(), and sum() values. Then use case to determine what values to display.
Since your problem statement and sample results do not match, I followed your sample results to return max() on an odd sum(). You can switch this by changing the two case statements from 1 to 0.
Working fiddle
with totals as (
select sum(marks1) as marks1sum,
min(marks1) as marks1min,
max(marks1) as marks1max,
sum(marks2) as marks2sum,
min(marks2) as marks2min,
max(marks2) as marks2max
from numbers
)
select case mod(marks1sum, 2)
when 1 then marks1max
else marks1min
end as marks1,
case mod(marks2sum, 2)
when 1 then marks2max
else marks2min
end as marks2
from totals;
You are reusing marks1 and marks2 when aliasing your third and fourth column which is colliding. Try using different name.
I'm using the below command to find the sum of records from 8 columns but getting null in the O/P as shown below.
Command part 1
command part 2
Output
How can this be fixed?
Yes, the thing is NULL + something results NULL. To solve this, wrap each sum() in the NVL(sum(),0), so if some particular sum() is NULL, it is converted to 0 and the whole total will be not null:
nvl(sum(case when col1='something' then 1 else 0 end),0)+ ...
Or always use else 0, like in the first expression (H).
Wrapping with NVL() will solve the problem even if column comes from the join and the rows are absent and sum is NULL.
I was trying to get the nulls on doing a SUM() function on sql and I figured out that sql now consider nulls, so if a column has a different value and a null value the sum is good calculated. For example I have the column SUM_EXAMPLE with the different values: NULL - 3 - 4 - NULL - 6
So if I execute the next query: select sum(SUM_EXAMPLE) FROM TABLE T the result is 13 and not null.
And if I have another column SUM_COLUMNS only with NULL the result of select sum(SUM_COLUMNS) FROM TABLE T is NULL. It has been a change or a improvement of oracle so it does this function right without using functions like isNull or NVL?
Thank you
Aggregate functions (SUM, AVERAGE etc) generally ignore NULL values. Therefore if there is at least one non null value in the column, you will get a non null result.
If all values in a column being aggregated are null, there is pretty much no other option but to return null as the result.
Note that this is different to how scalar functions behave. For example: "Select x + y" will return null if either x, y or both are null. You will only get a non null result for this if both x and y have non-null values.
Based on one column within my query results (Value), I am trying to write an if/else statement based on the value held which will display the result the in an additional row.
For example, if I have a record of 2 within the value field, but I want to check whether it is above < 5. If the value is less than 5 I basically want the additional column to display a hardcoded value of 5, else display actual value.
Any help would be appreciated.
Use a case statement
select a.*,
case
when a.TheField < 5 then 5
else a.TheField
end as NewField
from MyTable a
You can use a case
select value, case when value < 5
then 5
else value
end as calculated_column
from your_table
I am using SQL Server 2005 BOXIR2.
My doubt, from universe table there is an eventcode having different types of codes like Enquiry,FollowUp,LostofSales,Contact,etc
I make a measure that is from object properties formula count(Tablename.EventCode)save and export it, when I used this EventCode in Webireport, it show values for paricular EventCode, but zero values are not read it show null blank as below example .
I WANT TO GET THE ZERO VALUES FOR WHICH IT IS IN BLANK(NULL).
count(Tablename.EventCode)
Enquiry,FollowUp,LostofSales,Contact
10 20 15
5 12 5
6 4 3
Can u please help me how to get get zero values for null,Formula
I'm not sure exactly what you are asking, but I think you may be looking for ISNULL()
SELECT ISNULL(table_name.column_name, 0)
will return 0 if table_name.column_name is null
If you're getting NULLs when performing an aggregate, it's probably because one of elements is NULL. All you need to do is coalesce those entries to a known value (such as zero).
SELECT COUNT(COALESCE(Tablename.EventCode, 0)) FROM Tablename