Select 其中一个字段的计数大于一

Question

I want to do something like this:

SELECT * 
  FROM db.table 
 WHERE COUNT(someField) > 1

How can I achieve this in MySql?

Answer 1

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...

Answer 2

SELECT username, numb from(
Select username, count(username) as numb from customers GROUP BY username ) as my_table
WHERE numb > 3

Answer 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

Answer 4

Here you go:

SELECT Field1, COUNT(Field1)
  FROM Table1 
 GROUP BY Field1
HAVING COUNT(Field1) > 1
ORDER BY Field1 desc

Answer 5

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)

Answer 6

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

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Answer 7

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.

Answer 8

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

Answer 9

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 

Answer 10

Maybe:

SELECT *
FROM [Table]
where field IN (
    select field
    from [Table]
    group by field
    having COUNT(field)>1 )

Answer 11

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.