I have a table with some readings that looks like this:
id foo bar baz qux
1 2 4 NULL 3
2 6 11 0 2
I want to calculate an average of some columns, not including null values in the count. Something like this pseudo-code:
select (foo+bar+baz)/countNonNulls(foo,bar,baz) AS result
FROM readings WHERE id=1;
I.e, my expected result is (2+4)/2 = 3.
Is there a way to do this in a single SQL query?
In MySQL, you can use:
select (coalesce(foo, 0) + coalesce(bar, 0) + coalesce(baz, 0) /
((foo is not null) + (bar is not null) + (baz is not null))
) as average
Note that this assumes that at least one value is not null, to prevent division by 0.
To handle the general case, you can use case:
select (case when coalesce(foo, bar, bz) is not null
then (coalesce(foo, 0) + coalesce(bar, 0) + coalesce(baz, 0) /
((foo is not null) + (bar is not null) + (baz is not null))
)
end) as average
try the where clause: where [nameColumn] is not null
Related
I am stuck at a point where i have to increment a string, and my strings are of type C001,SC001,B001
in my data base they are defined like
what i am trying to do do is write a query which check the previous highest code present into my db and the incriment it to +1
for example C001 -> C002,C009->C010,C099`->C100 and so on
Similarly for SC001->SC002,SC009->SC010,SC099->SC100 and so on
Similarly fro B001 -> B002,B009->B010,B099`->B100 and so on
I have a query which my friend has suggested me to use but that query only incriminating AAAA->AAAA01 , AAAA09->AAAA10
query is
SELECT id AS PrevID, CONCAT(
SUBSTRING(id, 1, 4),
IF(CAST(SUBSTRING(id, 5) AS UNSIGNED) <= 9, '0', ''),
CAST(SUBSTRING(id, 5) AS UNSIGNED) + 1
) AS NextID
FROM (
-- since you allow strings such as AAAA20 and AAAA100 you can no longer use MAX
SELECT id
FROM t
ORDER BY SUBSTRING(id, 1, 4) DESC, CAST(SUBSTRING(id, 5) AS UNSIGNED) DESC
LIMIT 1
) x
when i am replacing ID with CategoryCode it is giving me PrevID-C004 NextID-C00401 which is not my requirement i want PrevID-C004 and NextID->C005
NOTE i am using my sqlServer 5.1
Just try this one ,
SELECT
CategoryCode,CAST(CONCAT(LPAD(CategoryCode,1,0),LPAD(MAX(RIGHT(CategoryCode,
3)) + 1, 3, 0) ) AS CHAR),
FROM test
SELECT
SubCategoryCode,CAST(CONCAT(LPAD(SubCategoryCode,2,0),
LPAD(MAX(RIGHT(CategoryCode, 3)) + 1, 3, 0) ) AS CHAR),
FROM test
SELECT
BrandCode,CAST(CONCAT(LPAD(BrandCode,1,0), LPAD(MAX(RIGHT(BrandCode, 3)) +
1, 3, 0)) AS CHAR) FROM test
I would like to create a statement that is equivalent to (x - y == 0) ? return 0 : return 100 in MySQL. Something that might look like this:
SELECT id, [(integer_val - 10 == 0) ? 0 : 100] AS new_val FROM my_table
I want to compare an attribute in each row to a certain number, and if the difference between that number and the number in the row is 0, I want it to give me 0, otherwise, I want it to give me 100.
Example:
Applying this query on my_table (with 10 being the 'compared to' number):
id | integer_val
===================
1 10
2 10
3 3
4 9
Would return this:
id | new_val
===================
1 100
2 100
3 0
4 0
How can I do this?
Try this:
SELECT id, IF(integer_val = 10, 100, 0) AS new_val
FROM my_table;
OR
SELECT id, (CASE WHEN integer_val = 10 THEN 100 ELSE 0 END) AS new_val
FROM my_table;
Use case when statement:
select *, (case when integer_val = 10 then 100 else 0 end) as New_Val
from yourtable
Try using the IF function:
SELECT id, IF(integer_val - 10 = 0, 0, 100) AS new_val FROM my_table
(I stuck with your condition expression, but it can be simplified a bit since integer_value - 10 = 0 has exactly the same truth value as integer_value = 10.)
Note that the IF function is different from MySQL's IF statement used for stored programs.
I have a table with columns showing ranges, like
id from to
1 10 100
2 200 300
I have a query which will be a list of values, like 17, 20, 44, 288 etc.
Is it possible to have a result set which would include the where condition, so I get:
id from to input
1 10 100 7
1 10 100 20
1 10 100 144
2 200 300 288
Right now the code runs one query per where value and it works, and I'm looking to increase performance by combing it into one large multiple where clause, like
SELECT *
FROM table
WHERE (from<=7 AND start>=7)
OR (from<=20 AND start>=20)
OR (from<=144 AND start>=144)
OR (from<=288 AND start>=288)
What you want makes no sense regarding ranges.
7 and 144 has no compatible range yet you want to put then into the first range.
In a result set with lots of values listing you will probably get to many conditions.
What you can do is to put those values that isn't in a range to show without correspondence. Like this:
With the structure being:
create table test (
id integer,
vfrom integer,
vto integer
);
insert into test values
(1, 10, 100),
(2, 200, 300);
create table vals(
val integer
);
insert into vals values (7), (20), (144), (288);
You can use this query:
select val, id, vfrom, vto
from vals v left join
test t on ( t.vfrom <= v.val and t.vto >= v.val )
It will bring you:
7 null null null
20 1 10 100
144 null null null
288 2 200 300
see it here on fiddle: http://sqlfiddle.com/#!2/f68fd/8
Maybe it isn't what you want but it is more logical.
Sure there is a query for this. Trouble is we need a table for specific values to show up; and then there are sub-queries and union selects:
SELECT table.*, values.val AS input
FROM (SELECT 7 AS val UNION SELECT 20 AS val UNION SELECT 144 AS val UNION SELECT 288 AS val) as values
JOIN table ON table.from <= values.val AND table.to >= values.val
This should do the trick. Note that you only have to specify the column name in the first SELECT with in a UNION SELECT.
I will suppose you are using Java as your application language. You could build your query this way:
public String buildQuery(int[] myList) {
String queryToReturn = "";
for (int queryIndex = 0; queryIndex < myList.length; queryIndex++) {
queryToReturn += ((queryIndex == 0) ? ("") : (" union ")) +
"(select `id`, `from`, `to`, " + myList[queryIndex] + " as input
from MyTable
where `from` < " + myList[queryIndex] + " and " + myList[queryIndex] " < `to`)";
}
return queryToReturn;
}
Then run the returned query.
Well, I have a table data of millions of rows. I want to carry out correlation study for every row (from the 1st to the current row minus 1). For e.g. the 1st rows is omitted. The 2nd row's result column is to be supplied with the correlation using the 1st row. The 3rd row's result column is to be supplied with the correlation using the 1st and 2nd row. And so on.
Correlation for the entire table can be calculated using:
SELECT (Count(*)*Sum(x*y)-Sum(x)*Sum(y))/
(sqrt(Count(*)*Sum(x*x)-Sum(x)*Sum(x))*
sqrt(Count(*)*Sum(y*y)-Sum(y)*Sum(y))) AS TotalCorelation FROM Data;
I want to avoid using Joins as much as possible as it takes lots of time, sometimes even timeout error, above 300 seconds). What's the other alternative?
Example table Data Structure:
id, x, y, result
1 , 4, 2, null
2 , 6, 3, -0.2312
3 , 5, 5, 0.42312
4 , 6, 2, -0.5231
5 , 5, 5, 0.22312
6 , 3, 7, -0.2312
7 , 2, 9, 0.42231
8 , 7, 2, 0.32253
9 , 9, 5, 0.32431
id : primary key
x and y : The data
result: correlation
I think this is it:
SELECT d2.ID, d2.x, d2.y, d2.result,
(Count(*)*Sum(d1.x*d1.y)-Sum(d1.x)*Sum(d1.y))/
(sqrt(Count(*)*Sum(d1.x*d1.x)-Sum(d1.x)*Sum(d1.x))*
sqrt(Count(*)*Sum(d1.y*d1.y)-Sum(d1.y)*Sum(d1.y))) AS TotalCorelation
FROM Data d1
RIGHT JOIN Data d2 ON d1.id < d2.id
GROUP BY d2.ID
ORDER BY d2.ID
Without a closed form for calculating correlation of N+1 from N rows, you have to use a quadratic join like this.
I'm assuming that your basic formula is correct. But I'm not sure it is -- when I just run it on the total dataset, I don't get the result 0.32431, I get -0.552773693079.
Here's a linear implementation:
SET #SumX = 0;
SET #SumY = 0;
SET #Count = 0;
SET #SumX2 = 0;
SET #SumY2 = 0;
SET #SumXY = 0;
SELECT id, x, y,
#SumX := #SumX + x AS SumX,
#SumY := #SumY + y AS SumY,
#Count := #Count + 1 AS ct,
#SumX2 := #SumX2 + x*x AS SumX2,
#SumY2 := #SumY2 + y*y AS SumY2,
#SumXY := #SumXY + x*y AS SumXY,
IF(#Count > 1,
(#Count*#SumXY-#SumX*#SumY)/
(sqrt(#Count*#SumX2-#SumX*#SumX)*
sqrt(#Count*#SumY2-#SumY*#SumY)), NULL) AS TotalCorelation
FROM DATA
ORDER BY id
SQLFIDDLE
I need to concatenate from two different tables.
Compare s.panelid (result like "AA") to b.modulecodes and return number_of_strings. Then put s.panelid (result like "AA") and number_of_string together.
select concat(Mid(s.panelid, 5, 2), ' - ' , '??') as `Module Type-Strings`
from r2rtool.stringtopanel s, be.modulecodes b
where s.insertts > '2011-07-15' and s.insertts < '2011-07-26' and Mid(s.panelid, 5, 2) != 99
group by date(insertts), `Module Type-Strings`
order by `Module Type-Strings`;
Be (Table): modulecodes, number_of_strings
AA - 12
AB - 4
AD - 3
AE - 12
When I run the above query it returns things like: Module Type-Strings = 'AA-??' and "AB-??" of course.
I am looking for: Module Type-Strings = 'AA-12'
Just in case you haven't tried it already...
Have you tried this?
select concat(Mid(s.panelid, 5, 2), ' - ' , b.number_of_string) as `Module Type-Strings`
from r2rtool.stringtopanel s, be.modulecodes b
where s.insertts > '2011-07-15' and s.insertts < '2011-07-26' and Mid(s.panelid, 5, 2) != 99
group by date(insertts), `Module Type-Strings`
order by `Module Type-Strings`;
There I'm basically replacing the '??' with the column you are asking about, number_of_string in the be.modulecodes table (aliased as b in the from clause).