I want to do something like this:
SELECT *
FROM db.table
WHERE COUNT(someField) > 1
How can I achieve this in MySql?
Use the HAVING
, not WHERE
clause, for aggregate result comparison.
Taking the query at face value:
SELECT *
FROM db.table
HAVING COUNT(someField) > 1
Ideally, there should be a GROUP BY
defined for proper valuation in the HAVING
clause, but MySQL does allow hidden columns from the GROUP BY ...
Is this in preparation for a unique constraint on someField
? Looks like it should be...
SELECT username, numb from(
Select username, count(username) as numb from customers GROUP BY username ) as my_table
WHERE numb > 3
You can also do this with a self-join:
SELECT t1.* FROM db.table t1
JOIN db.table t2 ON t1.someField = t2.someField AND t1.pk != t2.pk
Here you go:
SELECT Field1, COUNT(Field1)
FROM Table1
GROUP BY Field1
HAVING COUNT(Field1) > 1
ORDER BY Field1 desc
One way
SELECT t1.*
FROM db.table t1
WHERE exists
(SELECT *
FROM db.table t2
where t1.pk != t2.pk
and t1.someField = t2.someField)
我在Sql中的两个表之间给出了一个示例:
Select cn.name,ct.name,count(ct.id) totalcity from city ct left join country cn on ct.countryid = cn.id Group By cn.name,ct.name Having totalcity > 2
As OMG Ponies stated, the having clause is what you are after. However, if you were hoping that you would get discrete rows instead of a summary (the "having" creates a summary) - it cannot be done in a single statement. You must use two statements in that case.
For me, Not having a group by just returned empty result. So i guess having a group by for the having statement is pretty important
Without HAVING<\/strong>
SELECT COL,TOTAL
FROM (SELECT SPORT, COUNT(COL) AS TOTAL FROM db.table GROUP BY SPORT)
WHERE TOTAL > 100 ORDER BY TOTAL
Maybe:
SELECT *
FROM [Table]
where field IN (
select field
from [Table]
group by field
having COUNT(field)>1 )
It should also be mentioned that the "pk" should be a key field. The self-join
SELECT t1.* FROM db.table t1
JOIN db.table t2 ON t1.someField = t2.someField AND t1.pk != t2.pk
by Bill Karwin give you all the records that are duplicates which is what I wanted. Because some have more than two, you can get the same record more than once. I wrote all to another table with the same fields to get rid of the same records by key fields suppression. I tried
SELECT * FROM db.table HAVING COUNT(someField) > 1
above first. The data returned from it give only one of the duplicates, less than 1/2 of what this gives you but the count is good if that is all you want.
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