N methods for querying duplicate data in Oracle

1. Search for redundant duplicate records in the Table. duplicate records are determined based on a single field (peopleid ).
Select * from people
Where peopleid in (select peopleid from people group by peopleid having count

(Peopleid)> 1)

2. Delete unnecessary duplicate records in the Table. Repeat records are determined based on a single field (eagleid), leaving only the records with the smallest rowid
Delete from people
Where peopleid in (select peopleid from people group by peopleid having count

(Peopleid)> 1)
And rowid not in (select Min (rowid) from people group by peopleid having count (peopleid

)> 1)

3. Search for redundant duplicate records in the table (multiple fields)
Select * From vitae
Where (A. peopleid, A. seq) in (select peopleid, seq from vitae group by peopleid, seq having

Count (*)> 1)

4. Delete redundant record (multiple fields) in the table, leaving only the records with the smallest rowid
Delete from vitae
Where (A. peopleid, A. seq) in (select peopleid, seq from vitae group by peopleid, seq having

Count (*)> 1)
And rowid not in (select Min (rowid) from vitae group by peopleid, seq having count (*)> 1)

5. Search for redundant duplicate records (multiple fields) in the table, excluding records with the smallest rowid
Select * From vitae
Where (A. peopleid, A. seq) in (select peopleid, seq from vitae group by peopleid, seq having

Count (*)> 1)
And rowid not in (select Min (rowid) from vitae group by peopleid, seq having count (*)> 1)

(2) For example, there is a field "name" in Table A, and the "name" values may be the same between different records,
Now, you need to query items with duplicate "name" values between records in the table;Select name, count (*) from a group by name having count (*)> 1

If the gender is also the same, the statement is as follows:
Select name, sex, count (*) from a group by name, sex having count (*)> 1

(3) method 1
Declare @ Max integer, @ ID integer
Declare cur_rows cursor local for Select Main field, count (*) from table name group by main field having

Count (*)>; 1
Open cur_rows
Fetch cur_rows into @ ID, @ Max
While @ fetch_status = 0
Begin
Select @ max = @ max-1
Set rowcount @ Max
Delete from table name where primary field = @ ID
Fetch cur_rows into @ ID, @ Max
End
Close cur_rows
Set rowcount 0

Method 2
There are two Repeated Records. One is a completely repeated record, that is, records with all fields being repeated, and the other is records with duplicate key fields, such as duplicate name fields, other fields are not necessarily repeated or can be ignored.

　　1. For the first type of repetition, it is easier to solve.
Select distinct * From tablename
You can get the result set without repeated records.
If the table needs to delete duplicate records (one record is retained), you can delete the record as follows:
Select distinct * into # TMP from tablename
Drop table tablename
Select * into tablename from # TMP
Drop table # TMP
The reason for this repetition is that the table design is not weekly. You can add a unique index column.

　　2. This type of repeat problem usually requires that the first record in the repeat record be retained. The operation method is as follows, assuming that there are repeated fields as name and address, the result set of the two fields must be obtained.

Select Identity (INT, 1, 1) as autoid, * into # TMP from tablename
Select min (autoid) as autoid into # tmp2 from # TMP group by name, autoid
Select * from # TMP where autoid in (select autoid from # tmp2)
The last select gets the result set with no duplicate name and address (but with one more autoid field, you can write
This column is omitted in the select clause)

(4) Duplicate queries
Select * From tablename where ID in (
Select ID from tablename
Group by ID
Having count (ID)> 1
)