I'm creating a new table and carrying over several columns from a previous table. One of the new fields that I need to create is a flag that will have values 0 or 1 and value needs to be determined based on 6 previous fields in the table.
The 6 previous columns have preexisting values of 0 or 1 stored for each one. This new field needs to check whether any of the 6 columns have 1 and if so set the flag to 0. If there is 0 in all 6 fields then set itself to 1.
Hopefully this makes sense. How can I get this done in oracle? I assume a case statement and some sort of forloop?
You can use greatest() function: GREATEST
create table t_new
as
select
case when greatest(c1,c2,c3,c4,c5,c6)=1 -- at least one of them contains 1
then 0
else 1
end c_new
from t_old;
Or even shorter:
create table t_new
as
select
1-greatest(c1,c2,c3,c4,c5,c6) as c_new
from t_old;
In case of greatest = 1, (1-1)=0, otherwise (1-0)=1
You can use a virtual column with a case expression; something like:
flag number generated always as (
case when val_1 + val_2 + val_3 + val_4 + val_5 + val_6 = 0 then 1 else 0 end
) virtual
db<>fiddle
or the same thing with greatest() as #Sayan suggested.
Using a virtual column means the flag will be right for newly-inserted rows, and if any of the other values are updated; you won't have to recalculate or update the flag column manually.
I've assumed the other six columns can't be null and are constrained to only be 0 or 1, as the question suggests. If they can be null you can add nvl() or coalesce() to each term in the calculation.
Related
Using Microsoft SQL Server, if you use COUNT(column name) it returns the number of rows in that column which have a non-null value (i.e., it counts the rows, ignoring nulls).
Is there any way to do something similar, but allowing you to tell it which values to ignore? For example, if I wanted to count all the rows in a table which have a value which is NOT 1, I could do something like COUNTNOT(column name,1). That would count all the rows in the specified column which have a value NOT 1.
You may use conditional aggregation:
SELECT COUNT(CASE WHEN some_val <> 1 THEN 1 END) AS cnt
FROM yourTable;
The above logic is that COUNT will count one whenever some value is not equal to 1. Otherwise, it falls on the ELSE conditional, which if not present defaults to the value NULL. Since NULL is not counted, any value other than 1 would contribute zero to the count.
Why not put what you want to exclude in a WHERE clause?
SELECT COUNT(some_val) AS cnt
FROM yourTable
WHERE some_val <> 1
You need to be careful about NULL values. I would recommend:
select sum(case when column in (<values to ignore>) then 0 else 1 end)
This will count NULL values as not in the list (even if NULL is in the list). To ignore NULL values (as well), switch the logic to:
select sum(case when column not in (<values to ignore>) then 1 else 0 end)
and be sure NULL is not in the list.
Given table:
ID ANOTHERID ONE TWO THREE
X1 B1 15 15 -
X1 B2 10 - -
X2 B1 - 20 -
This query:
SELECT SUM (ONE + TWO + THREE) FROM (TABLE)
GROUP BY ID, ANOTHERID
I also tried
select sum(coalesce( ONE + TWO + THREE, ONE + TWO, ONE + THREE, ONE +
THREE))
at least one column has a null value. How can I still add them even if there is a null? As null and 0 have different meanings here (null means not started, 0 means not worked), I dont want to replace null with 0. Thanks
One method is:
SELECT SUM(COALESCE(ONE, 0) + COALESCE(TWO, 0) + COALESCE(THREE, 0))
FROM (TABLE)
GROUP BY ID, ANOTHERID;
Or, if you have at least one non-NULL value in each column:
SELECT SUM(ONE) + SUM(TWO) + SUM(THREE)
The time reporting table(s) should not allow null values, and the employee table should have a hire date field which can be used as criteria in your reporting queries. This will enable you to accurately report what management expects.
This solution worked for me
select
case when coalesce(sum(ONE), sum(TWO), sum(THREE)) is null then null else
sum(nvl(ONE,0) + nvl(TWO,0) + nvl(THREE,0)) end as
TOTALSUM
GROUP BY ID, ANOTHERID;
You might need to add another column in your table that describes the status of the employee (new, old) then make a condition like this:
if emp_status = 'new' then
--some code
working_hours := null;
else
--some code
working_hours : 0;
end if;
I want to take a value from a selected column to operate the next column. For example:
SELECT CASE
WHEN ID < 4 THEN ID
ELSE 10
END
AS MY_ID,
MY_ID + 5 AS EXTRA_ID
FROM FOO
That would output for IDs 1,2,3,4,5:
MY_ID EXTRA_ID
1 6
2 7
3 8
10 15
10 15
If I do MY_ID + 5 it will complain about MY_ID not existing (it's an alias, so it makes sense) and ID + 5 will read 1+5, 2+5, 3+5, 4+5, 5+5 instead of 1+5, 2+5, 3+5, 4+10, 5+10 when it goes through the ELSE. Is it even possible to do this? I'm doing it in SSRS - Report builder, and need to operate a result that might be set to a defualt value depending on the CASE clause.
You can repeat the same CASE expression with +5 in the end for the extra_id column
SELECT CASE
WHEN ID < 4 THEN ID
ELSE 10
END
AS MY_ID,
CASE
WHEN ID < 4 THEN ID
ELSE 10
END + 5 AS EXTRA_ID
FROM FOO
An alternative is to create the extra_id column value inside SSRS using an expression
= Fields!my_id.value + 5
you cannot reuse the calculation in the same level. Using my_id in the where clause will fail as well. Either you have to calucate it multiple times, place another select around your statement or use a with statement (CTE).
Simply wrap it with another select:
SELECT t.*,
t.my_id + 5 as extra_id
FROM(Your Query) t
Derived columns are not available in the same layer they're being created. By wrapping them with another select, you make them available (that because the inner query is being processed before the outer) .
You just need a subquery to create MY_ID before doing anything with it. By creating MY_ID in the inner query the outer query can use to define new fields.
SELECT
a.MY_ID,
a.MY_ID + 5 AS EXTRA_ID
from
(SELECT
CASE
WHEN ID < 4 THEN ID
ELSE 10
END
AS MY_ID
FROM FOO) as a
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
Given table:
ID ONE TWO
X1 15 15
X2 10 -
X3 - 20
This query:
SELECT (ONE + TWO) FROM (TABLE)
Just returns the sum of X1's values but not the others since at least one column has a null value. How can I still add them even if there is a null? i.e. consider the null as a 0 maybe?
SELECT (COALESCE(ONE, 0) + COALESCE(TWO, 0)) FROM (TABLE)
COALESCE will return the first non-null value found in the parameters from left to right. So, when the first field is null, it will take the 0.
That way, X2 will result in 10 + 0 = 10
there is already a good answer, but I think it is worth mention to the antonpug (in case he doesn't know) that the reason why this is happening is that NULL is not a value that can be compared or summed.
NULL isn't 0 or '' (empty string), so every operation involving NULL will result NULL (10 + NULL = NULL), even (NULL=NULL) will evaluate to FALSE