Say I had two tables in SQL. Now I would like to get the quotient of the count of table 1 and count of table 2. How can I do that?
In Short:
(# of rows in table 1) / (# of rows in table 2)
EDIT:
This is what I tried:
SELECT COUNT(t1.a) / COUNT(t2.a)
FROM table1 t1, table2 t2
Here's one way to get the result:
SELECT c1.cnt / c2.cnt AS q
FROM ( SELECT COUNT(1) AS cnt
FROM table1
) c1
CROSS
JOIN ( SELECT COUNT(1) AS cnt
FROM table2
) c2
Another way to get an equivalent result:
SELECT (SELECT COUNT(1) FROM table1) / (SELECT COUNT(1) FROM table2) AS q
I would prefer the first query if I also needed to return the counts from the tables as separate columns in the resultset, for example:
SELECT c1.cnt AS table1_count
, c2.cnt AS table2_count
, c1.cnt / c2.cnt AS q
FROM ...
Try this:
SELECT COUNT(table1.column) as 'Table 1 Count'
,COUNT(table2.column) as 'Table 2 Count'
,COUNT(table1.column) / COUNT(table2.column) as 'Quotient'
FROM table1, table2
with
Ctable1 as
(select count(*) as num1 from table1),
Ctable2 as
(select count(*) as num2 from table2)
select num1 / num2 as quotient
from Ctable1,Ctable2
Remember:
When you count column, rows with "NULL" data will NOT count. (If you use Oracle, you can use count(a.*)
Int division in sql like most languages, returns int. (5/2 = 2 and not 2.5).
Related
I have a few tables in my DB. Let's call them table1, table2, table3.
All of them have a column named value.
I need to create a query that will return a single number, where this number is the sum of all the value columns from all the tables together...
I've tried the following way:
SELECT (SELECT SUM(value) FROM table1) + (SELECT SUM(value) FROM table2) + (SELECT SUM(value) FROM table3) as total_sum
But when at least one of the inner SUM is NULL, the entire total value (total_sum here) is NULL, so that's not very trustworthy.
When there is no value in a certain inner SUM query, I need it to return 0, so it doesn't affect the rest of the SUM.
To make it more clear, let's say I have the following 2 tables:
TABLE1:
ID | NAME | VALUE
1 Name1 1000
2 Name2 2000
3 Name3 3000
TABLE2:
ID | NAME | VALUE
1 Name1 1500
2 Name2 2500
3 Name3 3500
Eventually, the query I need will return a single value - 13500, which is the total sum of all the values under the VALUE column of all the tables here.
All the other columns have no meaning for the needed query, and I even don't care much for performance in this case.
You can achieve it using Coalesce as follows
SELECT
(SELECT coalesce(SUM(value),0) FROM table1) +
(SELECT coalesce(SUM(value),0) FROM table2) +
(SELECT coalesce(SUM(value),0) FROM table3) as total_sum
Another approach is to use union all to merge all values into single table
select distinct coalesce(sum(a.value), 0) as total_sum from
(select value from table1
union all
select value from table 2
union all
select value from table 3) a;
You can use the ISNULL function to take care of the NULLs.
SELECT ISNULL((
SELECT SUM(value) FROM table1
)
, 0
) + ISNULL((
SELECT SUM(value) FROM table2
)
, 0
) + ISNULL((
SELECT SUM(value) FROM table3
)
, 0
) AS total_sum;
You could simply sum all of them:
select sum(total) as Total
from (
select sum(value) as total from Table1
union all
select sum(value) as total from Table2
union all
select sum(value) as total from Table3
) t;
SELECT AS, COUNT(*)
FROM Table1
HAVING COUNT(AS)>1
group BY AS;
This produces the result
AS COUNT
5 2
I then want to use the AS value in another query and only output the end result. Is this possible.i was thinking something like.
SELECT *
FROM
TABLE 2
Where AS =(
SELECT AS, COUNT(*)
FROM Table1
HAVING COUNT(AS)>1
group BY AS;
);
This is called a subquery. To be safe, you would use in instead of = (and as is a bad name for a column, because it is a SQL key word):
SELECT *
FROM TABLE2
WHERE col IN (SELECT col
FROM Table1
GROUP BY col
HAVING COUNT(col) > 1
);
Your first query is also incorrect, because the having clause goes after the group by.
You could use a subquery with the in operator:
SELECT *
FROM table2
WHERE AS IN (SELECT AS
FROM table1
GROUP BY AS
HAVING COUNT(*) > 1)
I need to count rows in more than one table in SQL Server 2008. I do this:
select count(*) from (select * from tbl1 union all select * from tbl2)
But it gives me an error of incorrect syntax near ). Why?
PS. The actual number of tables can be more than 2.
In case you have different number of columns in your tables try this way
SELECT count(*)
FROM (
SELECT NULL as columnName
FROM tbl1
UNION ALL
SELECT NULL
FROM tbl2
) T
try this:
You have to give a name to your derived table
select count(*) from
(select * from tbl1 union all select * from tbl2)a
I think you have to alias the SELECT in the FROM clause:
select count(*)
from
(
select * from tbl1
union all
select * from tbl2
) AS SUB
You also need to ensure that the * in both tables tbl1 and tbl2 return exactly the same number of columns and they have to be matched in their type.
I don't like doing the union before doing the count. It gives the SQL optimizer an opportunithy to choose to do more work.
AlexK's (deleted) solution is fine. You could also do:
select (select count(*) from tbl1) + (select count(*) from tbl2) as cnt
What is the method in T-SQL to select the orginal values limited by a HAVING attribute. For example, if I have
A|B
10|1
11|2
10|3
How would I get all the values of B (Not An Average or some other summary stat), Grouped by A, having a Count (Occurrences of A) greater than or equal two 2?
Actually, you have several options to choose from
1. You could make a subquery out of your original having statement and join it back to your table
SELECT *
FROM YourTable yt
INNER JOIN (
SELECT A
FROM YourTable
GROUP BY
A
HAVING COUNT(*) >= 2
) cnt ON cnt.A = yt.A
2. another equivalent solution would be to use a WITH clause
;WITH cnt AS (
SELECT A
FROM YourTable
GROUP BY
A
HAVING COUNT(*) >= 2
)
SELECT *
FROM YourTable yt
INNER JOIN cnt ON cnt.A = yt.A
3. or you could use an IN statement
SELECT *
FROM YourTable yt
WHERE A IN (SELECT A FROM YourTable GROUP BY A HAVING COUNT(*) >= 2)
A self join will work:
select B
from table
join(
select A
from table
group by 1
having count(1)>1
)s
using(A);
You can use window function (no joins, only one table scan):
select * from (
select *, cnt=count(*) over(partiton by A) from table
) as a
where cnt >= 2
I'm trying to get 2 counts from 2 tables and work out the percentage like for a MySQL db:
select field_one, count(*) as COUNT_ONE from table1 group by field_one;
select other_field,count(*) as COUNT_TWO from table2 group by other_field;
I want to combine the results and have FINAL_COUNT=(COUNT_ONE/COUNT_TWO) * 100 for percentage ?
quick and dirty:
select (a.count_one / b.count_two) * 100 as final_count from
(select field_one, count(*) as count_one from table1 group by field_one) a,
(select field_two, count(*) as count_two from table2 group by field_two) b
where a.field_one = b.field_two
select sum(((QUERY FROM TABLE 1) / (QUERY FROM TABLE 2)) * 100) as percentage