I hope I can get some help here since i cannot think of anything else.
so i have 2 results that come from the same table which i want to see in one query... so i used UNION, all good until there, now i need the difference between these two results. Let's say i have the next result:
measure 30_days
old_purchases 342
new_purchases 54
i need a new row that gives me the difference between those two, something like that:
measure 30_days
old_purchases 342
new_purchases 54
difference 288
You can use conditional aggregation:
select measure, value
from t
union all
select 'difference',
sum(case when measure = 'old_purchases' then value
when measure = 'new_purchases' then - value
else 0
end)
from t;
If you actually want to add this to the table then use insert:
insert into t (measure, value)
select 'difference',
sum(case when measure = 'old_purchases' then value
when measure = 'new_purchases' then - value
else 0
end)
from t;
Related
I'm selecting some data;
select c.*,
coalesce(s.column1, ...),
coalesce(s.column2, ...),
FROM
(SELECT ...)
Basically, if s.column1 or s.column2 is null then I am putting in some logic to take the average of that column and use it instead.
I want to have another field so I can know weather or not that value was computing using the average or not - perhaps a boolean? Lets say the average for column1 was 120, the table would look like;
column1 column2 avg
54 10 0
200 40 0
120 180 1
499 160 0
This allows me to see that the third row was generated using the avg of all rows as it was initially null.
How could the logic for the avg column work?
Your question seems fairly moot to me because:
The AVG function ignores NULL values by default, so the average using the overall average for NULL slots is the same as leaving out those slots entirely, and
If you just want to mark the rows which had a NULL value, you can use a CASE expression
So, to get what you want, just use this:
SELECT
column1,
column2,
CASE WHEN column1 IS NULL THEN 1 ELSE 0 END AS avg
FROM yourTable;
And know that SELECT AVG(column1) FROM yourTable would return the same value whether NULL rows were omitted, or the overall average were used.
How can I multiply all numbers in one column?
for example:
Status(finished or not finished)
1
1
1
1
0
I know how to use sum.
sum(Status)=4
I need some thing like sum for multiply
mul(status)=0
do we have something like mul(status)?
I don't know of a multiply aggregate function. However, in the case of a column containing only zeroes and ones the product will be one only if every value be one, otherwise it will be zero:
SELECT
CASE WHEN SUM(status) = COUNT(status) THEN 1 ELSE 0 END AS product
FROM yourTable
CASE WHEN SUM(status) = COUNT(status) THEN 1 ELSE 0 END AS product
I have a database with roughly 6 million entries - and will grow - where I'm running queries to return for a HighCharts charting functionality. I need to read longitudinally over years, so I'm running queries like this:
foreach($states as $state_id) { //php code
SELECT //mysql psuedocode
sum(case when mydatabase.Year = '2003' then 1 else 0 end) Year_2003,
sum(case when mydatabase.Year = '2004' then 1 else 0 end) Year_2004,
sum(case when mydatabase.Year = '2005' then 1 else 0 end) Year_2005,
sum(case when mydatabase.Year = '2006' then 1 else 0 end) Year_2006,
sum(case when mydatabase.Year = '2007' then 1 else 0 end) Year_2007,
sum(case when mydatabase.Year = '$more_years' then 1 else 0 end) Year_$whatever_year,
FROM mytable
WHERE State='$state_id'
AND Sex IN (0,1)
AND Age_segment IN (5,4,3,2,1)
AND "other_filters IN (etc, etc, etc)
} //end php code
But for various state at once... So returning lets say 5 states, each with the above statement but a state ID is substituted. Meanwhile the years can be any number of years, the Sex (male/female/other) and Age segment and other modifiers keep changing based on filters. The queries are long (at minimum 30-40seconds) a piece. So a thought I had - unless I'm totally doing it wrong - is to actually store the above query in a second table with the results, and first check that "meta query" and see if it was "cached" and then return the results without reading the db (which won't be updated very often).
Is this a good method or are there potential problems I'm not seeing?
EDIT: changed to table, not db (duh).
Table structure is:
id | Year | Sex | Age_segment | Another_filter | Etc
Nothing more complicated than that and no joining anything else. There are keys on id, Year, Sex, and Age_segment right now.
Proper indexing is what is needed to speed up the query. Start by doing an "EXPLAIN" on the query and post the results here.
I would suggest the following to start off. This way avoids the for loop and returns the data in 1 query. Not knowing the number of rows and cardinality of each column I suggest a composite index on State and Year.
SELECT mytable.State,mytable.Year,count(*)
FROM mytable
AND Sex IN (0,1)
AND Age_segment IN (5,4,3,2,1)
AND "other_filters IN (etc, etc, etc)
GROUP BY mytable.State,mytable.Year
The above query can be further optimised by checking the cardinality of some of the columns. Run the following to get the cardinality:
SELECT Age_segment FROM mytable GROUP BY Age_segment;
Pseudo code...
SELECT Year
, COUNT(*) total
FROM my_its_not_a_database_its_a_table
WHERE State = $state_id
AND Sex IN (0,1)
AND Age_segment IN (5,4,3,2,1)
GROUP
BY Year;
I have tried searching all over for answers but none have answered my exact issue. I have what should be a relatively simple query. However, I am very new and still learning SQL.
I need to query two columns with different dates. I want to return rows with the current number of accounts and current outstanding balance and in the same query, return rows for the same columns with data 90 days prior. This way, we can see how much the number of accounts and balance increased over the past 90 days. Optimally, I am looking for results like this:
PropCode|PropCat|Accts|AcctBal|PriorAccts|PriorBal|
----------------------------------------------------
77 |Comm | 350 | 1,000| 275 | 750
Below is my starting query. I realize it's completely wrong but I have tried numerous different solution attempts but none seem to work for my specific problem. I included it to give an idea of my needs. The accts & AcctBal columns would contain the 1/31/14 data. The PriorAcct & PriorBal columns would contain the 10/31/13 data.
select
prop_code AS PropCode,
prop_cat,
COUNT(act_num) Accts,
SUM(act_bal) AcctBal,
(SELECT
COUNT(act_num)
FROM table1
where date = '10/31/13'
and Pro_Group in ('BB','FF')
and prop_cat not in ('retail', 'personal')
and Not (Acct_Code = 53 and ACTType in (1,2,3,4,5,6,7))
)
AS PriorAccts,
(SELECT
SUM(act_bal)
FROM table1
where date = '10/31/13'
and Pro_Group in ('BB','FF')
and prop_cat not in ('retail', 'personal')
and Not (Acct_Code = 53 and ACTType in (1,2,3,4,5,6,7))
)
AS PriorBal
from table1
where date = '01/31/14'
and Pro_Group in ('BB','FF')
and prop_cat not in ('retail', 'personal')
and Not (Acct_Code = 53 and ACTType in (1,2,3,4,5,6,7))
group by prop_code, prop_cat
order by prop_cat
You can use a CASE with aggregates for this (at least in SQL Server, not sure about MySQL):
...
COUNT(CASE WHEN date='1/31/14' THEN act_num ELSE NULL END) as 'Accts'
,SUM(CASE WHEN date='1/31/14' THEN act_bal ELSE NULL END) as 'AcctBal'
,COUNT(CASE WHEN date='10/31/13' THEN act_num ELSE NULL END) as 'PriorAccts'
,SUM(CASE WHEN date='10/31/13' THEN act_bal ELSE NULL END) as 'PriorAcctBal'
....
WHERE Date IN ('1/31/14', '10/31/13')
I need to compare 2 columns in a table and give 3 things:
Count of rows checked (Total Rows that were checked)
Count of rows matching (Rows in which the 2 columns matched)
Count of rows different (Rows in which the 2 columns differed)
I've been able to get just rows matching using a join on itself, but I'm unsure how to get the others all at once. The importance of getting all of the information at the same time is because this is a very active table and the data changes with great frequency.
I cannot post the table schema as there is a lot of data in it that is irrelevant to this issue. The columns in question are both int(11) unsigned NOT NULL DEFAULT '0'. For purposes of this, I'll call them mask and mask_alt.
select
count(*) as rows_checked,
sum(col = col2) as rows_matching,
sum(col != col2) as rows_different
from table
Note the elegant use of sum(condition).
This works because in mysql true is 1 and false is 0. Summing these counts the number of times the condition is true. It's much more elegant than case when condition then 1 else 0 end, which is the SQL equivalent of coding if (condition) return true else return false; instead of simply return condition;.
Assuming you mean you want to count the rows where col1 is or is not equal to col2, you can use an aggregate SUM() coupled with CASE:
SELECT
COUNT(*) AS total,
SUM(CASE WHEN col = col2 THEN 1 ELSE 0 END )AS matching,
SUM(CASE WHEN col <> col2 THEN 1 ELSE 0 END) AS non_matching
FROM table
It may be more efficient to get the total COUNT(*) in a subquery though, and use that value to subtract the matching to get the non-matching, if the above is not performant enough.
SELECT
total,
matching,
total - matching AS non_matching
FROM
(
SELECT
COUNT(*) AS total,
SUM(CASE WHEN col = col2 THEN 1 ELSE 0 END )AS matching
FROM table
) sumtbl