Is there a way in MySQL to do a single SQL statement that returns the selected rows along with the count of the result rows?
I can do this:
SELECT COUNT(*) FROM BigTable WHERE firstname LIKE 'a%';
Which gives me a single result row with the count (37,781). I can get the actual row data like this:
SELECT firstname FROM BigTable WHERE firstname LIKE 'a%';
which displays the actual 37,781 rows. But when I try to combine them, like this:
SELECT firstname, COUNT(*) FROM BigTable WHERE firstname LIKE 'a%';
I get a single row with the first row that matches the query, and the total count of records that matches the query.
What I'd like to see is two columns with 37,781 rows. The first column should contain the first name for each row and the second column should contain the number '37,781' for every row. Is there a way to write the query to accomplish this?
You can use a CROSS JOIN. The subquery will get the count for all firstnames and then it will include this value in each row:
SELECT firstname, d.total
FROM BigTable
CROSS JOIN
(
SELECT COUNT(*) total
FROM BigTable
WHERE firstname LIKE 'a%'
) d
WHERE firstname LIKE 'a%';
See SQL Fiddle with Demo
You can join with a subquery:
SELECT firstname, ct
FROM BigTable
JOIN (SELECT COUNT(*) ct
FROM BigTable
WHERE firstname LIKE 'a%') x ON (1 = 1)
WHERE firstname LIKE 'a%'
The cross join is not the efficient way, the better way is to use an inline SELECT like the following structure:
SELECT firstname,
(select count(*) from BigTable where firstname like 'a%') as count
from BigTable
where firstname like 'a%'
I tested both approaches with 50k records in database, and this approach is almost 2x faster.
I feel like this used to be the case for older versions of MySQL, but this isn't working in my tests.
But according to the manual, http://dev.mysql.com/doc/refman/5.1/en/group-by-functions.html#function_count Given that COUNT(*) is a group by function, and naturally groups all of the rows together, when a GROUP BY statement is not attached, I can only see the solution to this being either multiple statements, or a sub-query. I would suggest running the 2 queries separately, if you can, but if that isn't possible, Try:
SELECT firstname,
total
FROM BigTable,
( SELECT COUNT(*) AS total
FROM BigTable ) AS dummy
WHERE firstname LIKE 'a%';
Related
How can I create a query to SELECT ALL DB WITHOUT duplicates
Like (old DB that is no longer in use c,f,g. basically if it does have eur and has an original name than it is relevant):
a
b
c
ceur
d
f
feur
g
geur
I need it to be like:
a
b
ceur
d
feur
geur
Many thanks...
SELECT DISTINCT
is what you're looking for. See more here.
For instance, let's say you have a table that contains the following rows:
name, city, address, country.
You now wish to get the countries that has been stored, without duplicates. Multiple people might come from the same country, and so the table would most likely have duplicate entries of that country.
How you achieve this is by using the SELECT DISTINCT.
Example:
SELECT DISTINCT country FROM table_name;
What this will do is retreive the country row without duplicates. That way, you can see which countries are actually stored in that table without duplicates.
If you have multiple databases (I don't know if that's what you were getting at), then you will need to perform a JOIN on the relevant tables, given you have access to them all. I would recommend doing a LEFT JOIN if you are to join more than just 1 extra table.
Example:
SELECT DISTINCT table_name.row_name, table_name.row_name2, table_name.row_name3
FROM table_name
LEFT JOIN table_name2 ON table_name.row_name = table_name2.row_name
LEFT JOIN table_name3 ON table_name2.row_name = table_name3.row_name
[...]
WHERE table.row_name = 'value';
Can you query information_schema.TABLES and distinct in the select, plus a predicate to filter out whatever you don't want?
You can do:
select t.*
from t
where name like '%eur'
union all
select t.*
from t
where not like '%eur' and
not exists (select 1 from t t2 where t2.name = concat(t.name, 'eur');
Ive got a table like this, where I'm looking for unnecessary duplicate rows:
I want to find any rows where the First Name, Last Name, and Occupation columns are identical - in this case rows 1 and 3. I don't want to specify what the identical values should be as I dont know.
I've tried the answer to this question, but I dont think it applies to this case.
simple solution is to add a HAVING clause where there are duplicates after grouping by all three columns
SELECT
ID, FirstName, LastName, Occupation, Age
FROM table1
GROUP BY
FirstName,
LastName,
Occupation
HAVING COUNT(*) > 1
here is a DEMO with two duplicate rows to ensure it works properly
EDIT:
my first understanding was you wanted one row returned when it has duplicates.. if you want a query that will return all duplicate rows..
then here it is... this will return rows 1 and 3
SELECT p1.* FROM people p
JOIN people p1
ON p1.firstname = p.firstname
AND p1.lastname = p.lastname
AND p1.occupation = p.occupation
GROUP BY id
HAVING COUNT(*) > 1;
another DEMO
Self join, 3 times (untested): SELECT a.* from your_table a, your_table b, your_table c, your_table d
where
a.fname = b.fname and a.lname=c.lname and a.occupation=d.occupation
I have the following table:
CREATE TABLE sometable (my_id INTEGER PRIMARY KEY AUTOINCREMENT, name STRING, number STRING);
Running this query:
SELECT * FROM sometable;
Produces the following output:
1|someone|111
2|someone|222
3|monster|333
Along with these three fields I would also like to include a count representing the amount of times the same name exists in the table.
I've obviously tried:
SELECT my_id, name, count(name) FROM sometable GROUP BY name;
though that will not give me an individual result row for every record.
Ideally I would have the following output:
1|someone|111|2
2|someone|222|2
3|monster|333|1
Where the 4th column represents the amount of time this number exists.
Thanks for any help.
You can do this with a correlated subquery in the select clause:
Select st.*,
(SELECT count(*) from sometable st2 where st.name = st2.name) as NameCount
from sometable st;
You can also write this as a join to an aggregated subquery:
select st.*, stn.NameCount
from sometable st join
(select name, count(*) as NameCount
from sometable
group by name
) stn
on st.name = stn.name;
EDIT:
As for performance, the best way to find out is to try both and time them. The correlated subquery will work best when there is an index on sometable(name). Although aggregation is reputed to be slow in MySQL, sometimes this type of query gets surprisingly good results. The best answer is to test.
Select *, (SELECT count(my_id) from sometable) as total from sometable
I wish to find the total number of distinct records in a table.
I have a table with the following columns
id, name, product, rating, manufacturer price
This has around 128 rows with some duplicates based on different column names.
I only want to select distinct rows:
select distinct name, product, rating, maufacturer, price from table
This returns 47 rows
For pagination purposes, I need to find the total number of distinct records, so I have another satatement:
select distinct count(name), product, rating, maufacturer, price from table
But this returns 128 instead of 47.
How can I get the total number of distinct rows? Any help will be much appreciated. Thanks
You have the distinct and count reversed.
SELECT COUNT(DISTINCT column_name) FROM table_name
Also, I would drop the extra fields when counting, your results will be unexpected for those other fields.
It is not quite clear if you want to get the count in the SAME query with the results or if you want to run a different query. Here go both solutions. In the result as a new column:
select distinct name, product, rating, manufacturer, price, (
select count(*) from (
select distinct name, product, rating, manufacturer, price from table1
) as resultCount) as resultCount
from table1
Notice the previous solution will repeat the count(*) for each row, which is not very efficient, not even visually appealing. Try running two queries one getting the actual data and the other one to get the amount of records in the table that match that data:
select distinct name, product, rating, manufacturer, price from table1
select count(*) from (
select distinct name, product, rating, manufacturer, price from table1
) as result
Hope this helps
Try adding GROUP BY name, product, rating, maufacturer, price clause
It would require running your actual query TWICE... an INNER for distinct and then get the count of those as a single row returned, and then join that to the original select distinct...
select distinct
t1.product,
t1.rating,
t1.maufacturer,
t1.price,
JustTheCount.DistCnt
from
table t1,
( select count(*) as DistCnt
from ( select distinct
t2.product,
t2.rating,
t2.maufacturer,
t2.price
from
table t2 )
) JustTheCount
In the following query, you're getting rows with distinct names since the DISTINCT clause precedes the name column:
SELECT DISTINCT name, product, rating, maufacturer, price FROM table
However, to get the count of the same records, use the following format:
SELECT COUNT(DISTINCT name) FROM table
Notice that DISTINCT goes inside of the COUNT function so that you're counting the distinct names. You probably don't want to include the other columns in the count query because they will be a random sample from the set. Of course, if you want a random sample, then include them.
Most applications will run the count query first, followed by the query to return the results. Also keep in mind that COUNT(*) is only an estimate, and the value may differ from the actual number of records returned.
SELECT DISTINCT COUNT(name), product FROM table isn't even a valid query in MySQL 4.x. You can't mix aggregate and non-aggregate columns. IN 5.x, it'll run, but the values for the non aggregate columns will be a random sample from the set.
At the risk of sparking some flames here.. you could always use:
SQL_CALC_FOUND_ROWS as the first part of your SQL. This is very mysql specific though.
http://dev.mysql.com/doc/refman/5.0/en/information-functions.html
mysql> SELECT SQL_CALC_FOUND_ROWS * FROM tbl_name
-> WHERE id > 100 LIMIT 10;
mysql> SELECT FOUND_ROWS();
I am trying to select of the duplicate rows in mysql table it's working fine for me but the problem is that it is not letting me select all the fields in that query , just letting me select the field name i used as distinct , lemme write the query for better understading
mysql_query("SELECT DISTINCT ticket_id FROM temp_tickets ORDER BY ticket_id")
mysql_query("SELECT * , DISTINCT ticket_id FROM temp_tickets ORDER BY ticket_id")
1st one is working fine
now when i am trying to select all fields i am ending up with errors
i am trying to select the latest of the duplicates let say ticket_id 127 is 3 times on row id 7,8,9 so i want to select it once with the latest entry that would be 9 in this case and this applies on all the rest of the ticket_id's
Any idea
thanks
DISTINCT is not a function that applies only to some columns. It's a query modifier that applies to all columns in the select-list.
That is, DISTINCT reduces rows only if all columns are identical to the columns of another row.
DISTINCT must follow immediately after SELECT (along with other query modifiers, like SQL_CALC_FOUND_ROWS). Then following the query modifiers, you can list columns.
RIGHT: SELECT DISTINCT foo, ticket_id FROM table...
Output a row for each distinct pairing of values across ticket_id and foo.
WRONG: SELECT foo, DISTINCT ticket_id FROM table...
If there are three distinct values of ticket_id, would this return only three rows? What if there are six distinct values of foo? Which three values of the six possible values of foo should be output?
It's ambiguous as written.
Are you looking for "SELECT * FROM temp_tickets GROUP BY ticket_id ORDER BY ticket_id ?
UPDATE
SELECT t.*
FROM
(SELECT ticket_id, MAX(id) as id FROM temp_tickets GROUP BY ticket_id) a
INNER JOIN temp_tickets t ON (t.id = a.id)
You can use group by instead of distinct. Because when you use distinct, you'll get struggle to select all values from table. Unlike when you use group by, you can get distinct values and also all fields in table.
You can use DISTINCT like that
mysql_query("SELECT DISTINCT(ticket_id), column1, column2, column3
FROM temp_tickets
ORDER BY ticket_id");
use a subselect:
http://forums.asp.net/t/1470093.aspx