MSQL select regardless of distinct or not distinct (count greater than zero) 
In the data in the question, there is no repeating id in table A. The
query should be returning only one row from A, then.
However, your query has an error. The second join should be back to the
first table, not the second:
SELECT a.col1, b.col1, c.col2
FROM a
LEFT JOIN b
ON b.id = a.id
LEFT JOIN c
ON c.id = a.id
WHERE a.id = 1
You had c.id = b.id and b.id could be NULL if there is no match in that
table.
Also, from your description, I wonder if a union would be the best
approach:
select a.col1, 'a'
from a
where id = 1
union all
select b.col1, 'b'
from b
where id = 1
union all
select c.col2, 'c'
from c
where id = 1

Distinct value of a column and do a count on each distinct value 
Considering the following example:
To get the unique values, and the occurrences of each unique value, you can
do the following:
The image is tiny, so here is are the formulas to typein and drag down:
FORMULAS
1. Type in the first cell of column B:
=IF(ISERROR(INDEX($A$2:$A$8,MATCH(0,INDEX(COUNTIF($B$1:B1,$A$2:$A$8),0,0),0))),"",INDEX($A$2:$A$8,MATCH(0,INDEX(COUNTIF($B$1:B1,$A$2:$A$8),0,0),0)))
Drag the formula down the column B. You will get a list of unique values.
2. Type in the first cell of column C:
=COUNTIF($A$2:$A$8,B2)
Drag the formula down the column C. You will get the number of occurrences
of each unique value.
RESULT
This is what you will get:

Mysql count and count distinct in same query 
COUNT(DISTINCT field) will do the job:
SELECT user_id,
job.job_id AS job_id,
job_link,
COUNT(job.click_ip) AS click_ip,
COUNT(DISTINCT job.click_ip) AS click_ip_distinct
FROM user JOIN job ON user.job_id = job.job_id
WHERE user.user_id =7
GROUP BY job_id
SQL Fiddle here: http://sqlfiddle.com/#!2/5e03e/2/0

Sql Distinct & count 
When pid, pname and description are the same (like in your example) then
group by will aggregate those results to one row.
select t.pid, t.pname, t.description, sum(t.qty) as qty
from tbltemptransaction t
group by t.pid, t.pname, t.description
Edit
select t.pid, sum(t.qty) as qty
from tbltemptransaction t
where pid = @userid
group by t.pid
@user id is a parameter for session("userid")
Final Edit
select t.pid, p.pname, p.description, sum(t.qty) as qty
from tbltemptransaction t
inner join tblproducts p on p.pid = t.pid
where t.userid = 3
group by t.pid, p.pname, p.description

How to Echo a Distinct Count in PHP? 
count(distinct style) is the only row and column returned. Try this:
$result = mysql_query("select count(distinct style) from bottles", $con);
$row = mysql_fetch_row($result);
$num_rows = $row[0];

How to COUNT DISTINCT on more than one column 
I don't know if it's the best way, but I normally concatenate the two
values, using a delimiter to enforce "distinctness", so they become one
expression, which Oracle can handle with COUNT DISTINCT:
SELECT "group_id",count(*) , count(distinct "p_id"  ''  "version")
FROM tbl
group by "group_id"

Distinct count for two columns 
You need a GROUP BY like this:
select Category, COUNT(*) as Count
from YourTable
GROUP BY Category;
SQLFIDDLE

Count the distinct words 
If you don't mind a slight variation in the given output then the
traditional approach is with sort and uniq:
$ sort file  uniq c
2 com.a.b
1 com.c.d
3 com.e.f
Otherwise use a scripting language that has associative arrays such as awk:
$ awk '{a[$0]++}END{for(k in a)print k,a[k]}' file
com.e.f 3
com.c.d 1
com.a.b 2
Pipe to sort for ordering:
$ awk '{a[$0]++}END{for(k in a)print k,a[k]}' file  sort
com.a.b 2
com.c.d 1
com.e.f 3

Select distinct value when count = 1 in SQL 
If you use a where clause then you would filter out other values what would
make the count inaccurate.
select fID_a
from tbl
group by fID_a
having count(*) = 1
and sum(case when fID_b = 1 then 1 else 0 end) = 1

Count distinct same names 
It's very basic SQL example, group by column + aggregating results
select
FirstName, count(*)
from Table1
group by FirstName

Get Distinct Rows Where Value in Row is Count > 1? 
Use Enumerable.First:
var GetSetRows = from DataRow dr in MyTable.Rows
group dr by dr.Field<string>("SetNumber") into grp
where grp.Count() > 1
select grp.First();

sum of distinct value count from one table 
if you have known number of degree, this could be done using static query,
SELECT Name,
SUM(CASE WHEN degree = 11 THEN 1 ELSE 0 END) `degree 11`,
SUM(CASE WHEN degree = 12 THEN 1 ELSE 0 END) `degree 12`,
SUM(CASE WHEN degree = 13 THEN 1 ELSE 0 END) `degree 13`
FROM tableName
GROUP BY Name
SQLFiddle Demo
OUTPUT
╔════════╦═══════════╦═══════════╦═══════════╗
║ NAME ║ DEGREE 11 ║ DEGREE 12 ║ DEGREE 13 ║
╠════════╬═══════════╬═══════════╬═══════════╣
║ Adam ║ 2 ║ 1 ║ 0 ║
║ Beny ║ 1 ║ 0 ║ 1 ║

How to SELECT COUNT DISTINCT? 
UPDATED
SELECT COUNT(DISTINCT
ROUND(CONVERT(DECIMAL(20, 4),
DATEDIFF(minute,
CONVERT(datetime, '20130101 00:00:00',
120),
CONVERT(datetime, date + ' ' + time, 120))) /
5, 0)) n
FROM table1
WHERE date = '20130622'
AND errcode = 'Scrubber Failure'
AND frequency = 1
Output:
 N 

 6 
Here is SQLFiddle demo.

Distinct count with multiple columns 
It sounds like you want to count only the records with minimum Relevancy
for each ID. Therefore, you can do (SQL Fiddle example):
SELECT Category, COUNT(1)
FROM Table1 t1
WHERE NOT EXISTS
(
SELECT 1
FROM Table1 t2
WHERE t2.ID = t1.ID
AND t2.Relevancy < t1.Relevancy
)
GROUP BY Category

SQL Server 2008 Count(Distinct? 
You probably want to treat dates as dates, rather than strings. You can
determine whether a particular timestamp is on a Friday  or the hour of a
timestamp  using DATEPART, without having to CONVERT it into a CHAR:
datename(weekday, timestamp_value)  returns Friday
datepart(weekday, timestamp_value)  returns either 5 or 6, depending on
the value of SET DATEFIRST. (Get Day of Week in SQL 2005/2008)
datepart(hour, timestamp_value)  returns hour part
Using these, you can test whether a timestamp is on Friday at or after noon
by checking if datepart(weekday, timestamp_value) = 6 and datepart(hour,
timestamp_value) >= 12.
bendataclear pointed out that you're using distinct on a case statement
which can only ever return 0 or 1, so your total will only ever be 0, 1, or
2. If

Select Count Distinct Syntax, vb.net 
MONTH(date) in mysql returns string. So you need to enclose with ' '.
sRetrieve = "SELECT COUNT (DISTINCT defect_code) FROM daily_data WHERE
MONTH(date)='" & select_month & "' AND YEAR(date)=" &
select_year;

Aggregate distinct count in LINQ  VB.NET 
Since PagedDataSource doesn't implement IEnumerable<T>, just
IEnumerable, you need to first use Cast to cast the sequence to a sequence
of the proper type. You'll need to know what the actual type of the
objects in the sequence are as you haven't mentioned what it is here.
Then just apply each operation one after the other:
(In C#:)
var query = table.Cast<YourTypeGoesHere>()
.Select(item => item.Column)
.Distinct()
.Count();

Count distinct elements and return only one 
I think the easiest is to join another select statement to get the total
number of rows and add that to your main SELECT statement.
SELECT data AS data, count.count
FROM data
JOIN (SELECT COUNT(DISTINCT(data)) AS count FROM data WHERE parameter =
"test") AS count
WHERE parameter = "test"
ORDER BY rand()
LIMIT 1;
Here's a SQL Fiddle

Query to get count of distinct value in MySQL 
select count(distinct column_whose_distinct_values_you_want_to_count)
from rbt_activation_details_log
where RADL_ACTIVE ='A'
group by RADL_REQUEST_MSISDN
You're grouping and counting on the same column, so this will always give
you 1 as result.
EDIT:
Then simply omit the group by clause
select count(distinct RADL_REQUEST_MSISDN)
from rbt_activation_details_log
where RADL_ACTIVE ='A'

Pandas aggregate count distinct 
How about either of:
>>> df
date duration user_id
0 20130401 30 0001
1 20130401 15 0001
2 20130401 20 0002
3 20130402 15 0002
4 20130402 30 0002
>>> df.groupby("date").agg({"duration": np.sum, "user_id":
pd.Series.nunique})
duration user_id
date
20130401 65 2
20130402 45 1
>>> df.groupby("date").agg({"duration": np.sum, "user_id": lambda
x: x.nunique()})
duration user_id
date
20130401 65 2
20130402 45 1

Scope of COUNT(DISTINCT ..) when used with GROUP BY 
This may actually depend on where DISTINCT is used. For example, SELECT
DISTINCT COUNT( would be different than SELECT COUNT(DISTINCT.
In this case, it will work as you want and get a count of distinct names in
each group (even if the names are not distinct across groups).

Hibernate HQL Count Distinct not working? 
This is how to do in Hibernate Criteria
Criteria crit = session.createCriteria(Rating.class)
.add(Restrictions.like("item", item)
.addOrder(Order.asc("user"))
.setProjection(
Projections.distinct(Projections.projectionList()
.add(Projections.property("user"), "user")))
.setResultTransformer(Transformers.aliasToBean(Rating.class));

SQL/Hive count distinct column 
Yes, it is almost correct. But you have one simple mistake. Your column
name is wrong inside COUNT.
SELECT columnA,columnB,COUNT(DISTINCT columnC) No_of_distinct_colC
from table_name
group by columnA,columnB

mysql COUNT DISTINCT multiple columnes with WHERE 
Are you looking for the count per pid? If so, this is a simpler query:
SELECT pid, SUM(location like '%a%') as As,
SUM(location like '%b%') as Bs,
SUM(location like '%c%') as Cs
FROM db.t
WHERE (date > @dt)
GROUP BY pid

Select distinct column, and a count of the entries 
CREATE TABLE tbl (`email` varchar(10));
INSERT INTO tbl (`email`)
VALUES
('a@b.com'),
('b@b.com'),
('c@b.com'),
('d@b.com'),
('e@b.com'),
('a@b.com'),
('b@b.com'),
('c@b.com'),
('c@b.com');
SELECT email, COUNT(*)
FROM tbl
GROUP BY email;
Result
 EMAIL  COUNT(*) 

 a@b.com  2 
 b@b.com  2 
 c@b.com  3 
 d@b.com  1 
 e@b.com  1 
See a demo

How to display Distinct Count in Access Textbox? 
Here's a link that loops through the selected records based on your
parameters from the Select statement. It uses the .RecordCount off a
recordset, but the kicker is the recorde must be accessed first (hence the
loop).

How to implement SQL query, max(count(distinct attribute_name)) 
Try
SELECT *
FROM
(
SELECT book_publisher, COUNT(DISTINCT book_author_id) author_count
FROM table1
GROUP BY book_publisher
ORDER BY author_count DESC
)
WHERE rownum = 1
or
WITH cte AS
(
SELECT book_publisher, COUNT(DISTINCT book_author_id) author_count
FROM table1
GROUP BY book_publisher
)
SELECT book_publisher
FROM cte
WHERE author_count =
(
SELECT MAX(author_count)
FROM cte
)
or with analytical functions
SELECT book_publisher, author_count
FROM
(
SELECT book_publisher,
COUNT(DISTINCT book_author_id) author_count,
DENSE_RANK() OVER (ORDER BY COUNT(DISTINCT book_author_id) DESC)
rank
FROM table1
GROUP BY book_publisher
)
WHERE rank = 1
Here is SQLFiddle demo

Count Number of Distinct Columns in a Row with tSQL 
Select Name,Count(*) From
(select Name,FieldA from test10
Union
select Name,FieldB from test10
union
select Name,FieldC from test10
Union
select Name,FieldD from test10)as a
Group by name

How to count distinct values in a sequence of four numbers from 0 to 10? 
A Set<Integer> such as a HashSet<Integer> could simplify things
since it would not allow duplicates. It will allow you to call the add
method on duplicates to the Set, but if the Set already contains the item,
the add method will do nothing other than return false. Getting the size()
of the set after adding all items, will tell you how many nonduplicate
items exist.

Show count of columns distinct values 
You need to use the iif function within the two additional columns. Here is
some pseudo code to get you started.
SELECT County
,sum(iif(TGTE = "L",1,0)) as [L_Count]
,sum(iif(TGTE = "H",1,0)) as [H_Count]
FROM MyTable
GROUP BY
COUNTY;

Get Count() for DISTINCT values for each field SQL Server 
You don't need the rank function, you can use a normal count with TOP 10:
SELECT TOP 10 phonenumber, [count] = COUNT(*)
FROM ozekiout
GROUP BY Phonenumber
ORDER BY [count] DESC;
If you want to include more than 10 results if there are ties e.g.
Phonenumber count
01111111111 18
01111111112 15
01111111113 15
01111111114 14
01111111115 13
01111111116 13
01111111117 12
01111111118 12
01111111119 10
01111111120 10
01111111121 10
01111111122 10
.... CUT OFF
01111111122 9
you can use:
SELECT TOP 10 WITH TIES phonenumber, [count] = COUNT(*)
FROM ozekiout
GROUP BY Phonenumber
ORDER BY [count] DESC;

Oracle/SQL  Need help optimizing COUNT DISTINCT query 
Firstly, verify that the columns you use in your WHERE clauses (and from
the COUNT DISTINCT) have indexes (or are primary/unique/foreign keys).
Secondly, check if you could add other WHERE clauses to replace the
DISTINCT in the COUNT, or even replace it with a COUNT(*) which is very
optimized.
Thirdly, you could try to move your count(distinct) to another join or even
a subquery and check if performances changes.

Count distinct value pairs in multiple columns in SQL 
Get all distinct id, name and address columns and count the resulting rows.
SELECT COUNT(*) FROM mytable GROUP BY id, name, address

R: count number of distinct values in a vector 
Here are a few ideas, all points towards your solution already being very
fast. length(unique(x)) is what I would have used as well:
x < sample.int(25, 1000, TRUE)
library(microbenchmark)
microbenchmark(length(unique(x)),
nlevels(factor(x)),
length(table(x)),
sum(!duplicated(x)))
# Unit: microseconds
# expr min lq median uq max neval
# length(unique(x)) 24.810 25.9005 27.1350 28.8605 48.854 100
# nlevels(factor(x)) 367.646 371.6185 380.2025 411.8625 1347.343 100
# length(table(x)) 505.035 511.3080 530.9490 575.0880 1685.454 100
# sum(!duplicated(x)) 24.030 25.7955 27.4275 30.0295 70.446 100

Getting Count Only of Distinct Value Combinations of multiple fields. 
The subquery/CTE method is the "right" way to do it.
A quick (in terms of typing but not necessarily performance) and dirty way
is:
select count(distinct customername+'###'+Planet)
from #Customer;
The '###' is to separate the values so you don't get accidental collisions.

Count number of Distinct days in query 
You can CAST as date
SELECT COUNT(DISTINCT CAST(StartDate AS DATE))
FROM Stats
WHERE StartDate >= '20130101' AND StartDate < '20140101'
Also use an unambiguous date format such as yyyymmdd and >= < not
BETWEEN.
Your current query would include the 31st December if there was a row with
exactly the value 20131231 00:00:00 but not any with different times on
that date. I doubt that is intentional.

SQL Server 2008 Count(Distinct CASE? 
You can't really count half things using count, so that is not the way to
go. But, you can do it with arithmetic. I think something like this:
select (count(distinct (case when DATENAME(weekday, a.ApptStart) <>
'Friday'
then cast(a.apptstart as date)
end)
) +
0.5 * count(distinct (case when DATENAME(weekday, a.ApptStart) =
'Friday'
then cast(a.apptstart as date)
end)
)
) as ScheduleDays
If the docs only work on Fridays for half a day, I don't think you need to
check for the time of the appointment. Of course, you can if you like by
adding it into the second count.
Note that to count days, I used the simpler syntax

Trying count distinct strings, whats going wrong 
The problem is not your read loop. It gets stuck in an infinite loop in
while(i!=input.size()){
Think carefully about your end condition, and the lines that change i:
i+=count2;continue;
i++;
Will i++ ever be executed? Will i ever exactly equal input.size()? If there
are repeated words? If there are not?
.
.
.
Ok, thought about it? I replaced that loop with this. The comments should
explain:
while(i < input.size())
{
// Store current string
distinct.push_back(input[i]);
// Skip same strings
int j = i;
while ( j < input.size() // Don't go too far
&& input[i] == input[j] ) // And only while duplicates
++j;
// Store a count of how many we skipped
count.push_back(ji);
// Move to the next *nonidentical* st

MySQL 5.6.13 count distinct result not match 
Because COUNT DISTINCT doesn't consider rows where exists a column value
NULL
I try the same query with my table. In my table in some rows there are
column with NULL value, so the result is different.
See this sample SQLFiddle

MySQL  Getting count of distinct values from 3 tables 
Just UNION the tables together and COUNT. The UNION will remove duplicates,
so a simple COUNT will do the trick  a COUNT DISTINCT won't be needed.
This will work if you want the count only; if you want other values the
query gets slightly more involved:
SELECT COUNT(*) FROM (
SELECT employee_no
FROM complete_shifts
WHERE date = '20130613'
UNION SELECT employee_no
FROM incomplete_shifts
WHERE date = '20130613'
UNION SELECT employee_no
FROM incomplete_shift_register
WHERE date = '20130613'
) AllShifts
