I have the following SQL select problem:
I have two columns positive threshold and negative threshold (among several other columns like name, ids.... ).
If their (absolute) value is the same (multiply by -1) then I want to select only the positive threshold as column [threshold].
If the values are different, I want to select two columns [positiveThreshold] and [negativeThreshold].
Thank you in advance.
select null as [threshold], positivethreshold, negativethreshold
from table
where negativethreshold is null
or (positivethreshold + negativethreshold) <> 0
union
select positivethreshold, null, null
from table
where (positivethreshold + negativethreshold) = 0
Related
I want to overwrite a number based on a few conditions.
Intended overwrite:
If a string (in the example I use is just a letter) occurs across 3 columns at least 2 times and the numerical column is more than some number, overwrite the numerical value OR
If another string occurs across 3 columns at least 2 times and the numerical column is more than some other number, overwrite the numerical value, else leave the numerical value unchanged.
The approach I thought of first, works but only if the table has one row. Could this be extended somehow so it could work on more rows? And if my approach is wrong, would you please direct me to the right one?
Please, see the SQL Fiddle
Any help is highly appreciated!
if letter a repeats at least 2 times among section_1,section_2,section_3 and number >= 3 then overwrite number with 3 or if letter b repeats at least 2 times among section_1,section_2,section_3 and number >= 8 write 8, else leave number unchanged
CREATE TABLE sections (
id int,
section_1 text,
section_2 text,
section_3 text,
number int
);
INSERT INTO sections VALUES
( 1, 'a', 'a', 'c', 5),
( 2, 'b', 'b', 'c', 9),
( 3, 'b', 'b', 'c', 4);
expected result:
id number
1 3
2 8
3 4
Are you looking for a case expression?
select (case when (section_1 = 'a')::int + (section_2 = 'a')::int + (section_3 = 'a')::int >= 2 and
other_col > threshold
then 'special'
end)
You can have additional when conditions. And include this in an update if you really wand to change the value.
A typical solution uses a lateral join to unpivot:
select s.*, x.number as new_number
from sections s
cross join lateral (
select count(*) number
from (values (s.section_1), (s.section_2), (s.section_3)) x(section)
where section = 'a'
) x;
This is a bit more scalable than repeating conditional expression, since you just need to enumerate the columns in the values() row constructor of the subquery.
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.
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 have a table inside a PostgreSQL database with columns c1,c2...cn. I want to run a query that compares each row against a tuple of values v1,v2...vn. The query should not return an exact match but should return a list of rows ordered in descending similarity to the value vector v.
Example:
The table contains sports records:
1,USA,basketball,1956
2,Sweden,basketball,1998
3,Sweden,skating,1998
4,Switzerland,golf,2001
Now when I run a query against this table with v=(Sweden,basketball,1998), I want to get all records that have a similarity with this vector, sorted by number of matching columns in descending order:
2,Sweden,basketball,1998 --> 3 columns match
3,Sweden,skating,1998 --> 2 columns match
1,USA,basketball,1956 --> 1 column matches
Row 4 is not returned because it does not match at all.
Edit: All columns are equally important. Although, when I really think of it... it would be a nice add-on if I could give each column a different weight factor as well.
Is there any possible SQL query that would return the rows in a reasonable amount of time, even when I run it against a million rows?
What would such a query look like?
SELECT * FROM countries
WHERE country = 'sweden'
OR sport = 'basketball'
OR year = 1998
ORDER BY
cast(country = 'sweden' AS integer) +
cast(sport = 'basketball' as integer) +
cast(year = 1998 as integer) DESC
It's not beautiful, but well. You can cast the boolean expressions as integers and sum them.
You can easily change the weight, by adding a multiplicator.
cast(sport = 'basketball' as integer) * 5 +
This is how I would do it ... the multiplication factors used in the case stmts will handle the importance(weight) of the match and they will ensure that those records that have matches for columns designated with the highest weight will come up top even if the other columns don't match for those particular records.
/*
-- Initial Setup
-- drop table sport
create table sport (id int, Country varchar(20) , sport varchar(20) , yr int )
insert into sport values
(1,'USA','basketball','1956'),
(2,'Sweden','basketball','1998'),
(3,'Sweden','skating','1998'),
(4,'Switzerland','golf','2001')
select * from sport
*/
select * ,
CASE WHEN Country='sweden' then 1 else 0 end * 100 +
CASE WHEN sport='basketball' then 1 else 0 end * 10 +
CASE WHEN yr=1998 then 1 else 0 end * 1 as Match
from sport
WHERE
country = 'sweden'
OR sport = 'basketball'
OR yr = 1998
ORDER BY Match Desc
It might help if you wrote a stored procedure that calculates a "similarity metric" between two rows. Then your query could refer to the return value of that procedure directly rather than having umpteen conditions in the where-expression and the order-by-expression.
I have a table which has 32 columns in an Oracle table.
Two of these columns are identity columns
the rest are values
I would like to get the average of all the value columns, which is complicated by the null (identity) columns. Below is the pseudocode for what I am trying to achieve:
SELECT
((nvl(val0, 0) + nvl(val1, 0) + ... nvl(valn, 0))
/ nonZero_Column_Count_In_This_Row)
Such that: nonZero_Column_Count_In_This_Row = (ifNullThenZeroElse1(val0) + ifNullThenZeroElse1(val1) ... ifNullThenZeroElse(valn))
The difficulty here is of course in getting 1 for any non-null column. It seems I need a function similar to NVL, but with an else clause. Something that will return 0 if the value is null, but 1 if not, rather than the value itself.
How should I go about about getting the value for the denominator?
PS: I feel I must explain some motivation behind this design. Ideally this table would have been organized as the identity columns and one value per row with some identifier for the row itself. This would have made it more normalized and the solution to this problem would have been pretty simple. The reasons for it not to be done like this are throughput, and saving space. This is a huge DB where we insert 10 million values per minute into. Making each of these values one row would mean 10M rows per minute, which is definitely not attainable. Packing 30 of them into a single row reduces the number of rows inserted to something we can do with a single DB, and the overhead data amount (the identity data) much less.
(Case When col is null then 0 else 1 end)
You could use NVL2(val0, 1, 0) + NVL2(val1, 1, 0) + ... since you are using Oracle.
Another option is to use the AVG function, which ignores NULLs:
SELECT AVG(v) FROM (
WITH q AS (SELECT val0, val1, val2, val3 FROM mytable)
SELECT val0 AS v FROM q
UNION ALL SELECT val1 FROM q
UNION ALL SELECT val2 FROM q
UNION ALL SELECT val3 FROM q
);
If you're using Oracle11g you can use the UNPIVOT syntax to make it even simpler.
I see this is a pretty old question, but I don't see a sufficient answer. I had a similar problem, and below is how I solved it. It's pretty clear a case statement is needed. This solution is a workaround for such cases where
SELECT COUNT(column) WHERE column {IS | IS NOT} NULL
does not work for whatever reason, or, you need to do several
SELECT COUNT ( * )
FROM A_TABLE
WHERE COL1 IS NOT NULL;
SELECT COUNT ( * )
FROM A_TABLE
WHERE COL2 IS NOT NULL;
queries but want it as a data set when you run the script. See below; I use this for analysis and it's been working great for me so far.
SUM(CASE NVL(valn, 'X')
WHEN 'X'
THEN 0
ELSE 1
END) as COLUMN_NAME
FROM YOUR_TABLE;
Cheers!
Doug
Generically, you can do something like this:
SELECT (
(COALESCE(val0, 0) + COALESCE(val1, 0) + ...... COALESCE(valn, 0))
/
(SIGN(ABS(COALESCE(val0, 0))) + SIGN(ABS(COALESCE(val1, 0))) + .... )
) AS MyAverage
The top line will return the sum of values (omitting NULL values) whereas the bottom line will return the number of non-null values.
FYI - it's SQL Server syntax, but COALESCE is just like ISNULL for the most part. SIGN just returns -1 for a negative number, 0 for zero, and 1 for a positive number. ABS is "absolute value".