I want to generate a SQL query to get null count in a particular column like
SELECT COUNT (column) AS count
FROM table
WHERE column = null ;
This is returning 0, but I want how many null values are present in that column like
SELECT COUNT (column) AS count
FROM table
WHERE column = 'some value';
which returns the count of the matched records
NULL value is special in that you cannot use = with it; you must use IS NULL instead:
SELECT COUNT (*) AS count FROM table where column IS null ;
This is because NULL in SQL does not evaluate as equal to anything, including other NULL values. Also note the use of * as the argument of COUNT.
You can use a conditional sum()
SELECT sum(case when column is null
then 1
else 0
end) AS count
FROM table
A different query but exact answer check it out
select count(*)-count(column) from table
please vote check this as answer if it helps you
To get exact output you can use below command as well -
SELECT COUNT (*) AS count FROM table where column IS null OR column='';
because some times only '' doesn't counted as NULL.
Related
SELECT MIN(column) FROM table;
will return minimum from nonnull elements.
I would like to write a query that will treat NULL as if it were the smallest value possible.
I have seen tricks with dates using a special value like here: https://stackoverflow.com/a/32240382/7810882
But what if the column is of type int and there is no special value that I can map NULL to?
You can do this using a case expression:
SELECT (CASE WHEN COUNT(*) = COUNT(COLUMN) THEN MIN(column) END)
FROM table;
Total number of records in table i1450:
Total number with condition where i.BROJ is equal to field REFERENCA in other table:
Shouldn't it return difference between last two results (which is 64) when I use NOT IN in WHERE clause?
Both of columns are of varchar type.
If you have any NULL values in the REFERENCA column from the FpsPmtOrderRQ table then the NOT IN clause will not work as expected - (the reason why)
A solution is to remove NULL values from the result returned by the subselect.
SELECT COUNT(*)
FROM i1450 j
WHERE i.BROJ NOT IN (SELECT REFERENCA FROM FpsPmtOrderRQ WHERE REFERENCA IS NOT NULL)
If the sub-query returns a null value, the IN will not be true. Do NOT EXISTS instead.
select count(*)
from i1450 i
where not exists (select 1 from FpsPmtOrderRQ f
where i.broj = f.REFERENCA)
I think you need to coalesce your field to handle nulls. That is probably why you get 0.
By doing:
where coalesce(I.BROJ,'n/a') not in (select coalesce(REFERENCA,'')
or something similar, you would exclude nulls, and return a proper count.
I have a Table BoxTrans
the table Contain Rows (ID,Date,FromBox,ToBox,Value)
I want to make a View like (ID,Date,Box,ValueIn,ValueOut)
select when frombox Give Value to ValueOut
and when tobox Give Value to ValueIN
You can use a CASE statement to check the value of a different column when populating a column. The below query will return your output as long as either ToBox or FromBox is NULL, if they are both not null you may get unexpected results.
SELECT ID,
Date,
COALESCE(ToBox,FromBox) as Box,
CASE WHEN ToBox IS NOT NULL THEN value ELSE NULL as ValueIn,
CASE WHEN FromBox IS NOT NULL THEN value ELSE NULL as ValueOut
FROM BoxTrans
In SQL Server, if my SELECT statement in a subquery returns no row, is then the result of the subquery equal to NULL? I made some research, but I am not sure about it.
Example:
IF (SELECT TOP 1 CLMN1 FROM SOMETABLE) IS NOT NULL THEN
....
I am asking to understand the behaviour of the if-statement above.
Looks like the answer is yes:
DECLARE #Test TABLE (Id INT)
INSERT INTO #Test VALUES (1)
SELECT * FROM #Test WHERE Id = 2
SELECT CASE WHEN (SELECT * FROM #Test WHERE Id = 2) IS NULL THEN 1 ELSE 0 END
EDIT: after you updated your question I think I should add that instead of checking if there are rows with IS NULL you should use the following that can be better optimised by the server:
IF EXISTS(SELECT * FROM #Test WHERE Id = 2)
BEGIN
-- Whatever
END
NULL means no value, for example that the "box" for a certain column in a certain row is empty. NO ROW means that there are no rows.
No, NULL is a column value that indicates that the value of that column for a given row has no valid value. There would have to be a row returned by your query for that row to contain NULL column values.
A query that returns no rows just means that no rows matched the predicate you used in the query and therefore no data was returned at all.
Edit: After the question was edited, my answer doesn't address the specific case called out in the question. Juan's answer above does.
Here's the scenario:
I have a table with 3 columns: 'KeyColumn', 'SubKeyColumn' and 'BooleanColumn', where the first two are the primary keys of the table.
For my query, I'd like to count the number of rows there are for any given value in 'KeyColumn', and I'd also like to know which ones have a value of true for 'BooleanColumn'. My initial thought was to create a query like this:
SELECT
COUNT(*)
,COUNT(CASE WHEN BooleanColumn = 1 THEN 1 ELSE 0 END)
FROM
MyTable
GROUP BY
KeyColumn
However, the 2nd part does not work (I'm not entirely sure why I thought it would to begin with). Is it possible to do something like this in one query? Or am I going to need to do multiple queries to make this happen?
Change COUNT to SUM in the 2nd part. ;)
... CASE WHEN BooleanColumn = 1 THEN 1 ELSE NULL END ...
COUNT counts the NON-NULL rows.
You could also do SUM(CAST(BooleanColumn AS TINYINT))