- Oracle Sql Delete From Query
- How To Remove Duplicates In Oracle
- How To Delete Duplicates In Oracle
- Delete Rows From Oracle Table
Summary: in this tutorial, you will learn how to find duplicate records in the Oracle Database.
Problem Statement: You want to write a common procedure to find and remove duplicates from any table and columns in Oracle. Solution: We can use Oracle’s internal ROWID value for uniquely identifying rows in a table along with the OLAP function rownumber with partition clause. SQL Tutorial: How To Delete Duplicate Records in SQL Oracle SQL Tutorial SQL Tutorial for beginners PLSQL Tutorial PLSQL Tutorial for beginners PL/SQL Tutor.
Let’s start by setting up a sample table for the demonstration.
Let’s remove duplicate rows from table. Following ways can be used to delete duplicate records from table. Here assume that ID column should be unique after deleting. Now we see how to delete the duplicate records from the DupTest table in different ways.
Delete duplicate records in oracle csv using oracle sql plus remove duplicates from sql tables sql to pare rows within two tables remove duplicates other transforms 4 Ways To Delete Duplicate Records In Oracle WikihowHow. In this case, you can use the rowid which is a physical locator that specifies where on storage Oracle stores the row. Because the rowid is unique to each row, you can use it to remove the duplicates as shown below: DELETE FROM fruits WHERE rowid NOT IN (SELECT MIN (rowid) FROM fruits GROUP BY fruitid, fruitname, color).
Setting up a sample table
First, the following statement creates a new table named
fruits
that consists of three columns: fruit id, fruit name, and color:Second, insert some rows into the
fruits
table:Third, query data from the
fruits
table:As you can see from the picture above, the
fruits
table has duplicate records with the same information repeated in both fruit_name
and color
columns.Finding duplicate rows using the aggregate function
To find duplicate rows from the
fruits
table, you first list the fruit name and color columns in both SELECT
and GROUP BY
clauses. Then you count the number of appearances each combination appears with the COUNT(*)
function as shown below:The query returned a single row for each combination of fruit name and color. It also included the rows without duplicates.
To return just the duplicate rows whose
COUNT(*)
is greater than one, you add a HAVING
clause as follows:So now we have duplicated record. It shows one row for each copy.
If you want to return all the rows, you need to query the table again as shown below:
Now, we have all duplicate rows displayed in the result set.
Finding duplicate records using analytic function
See the following query:
In this query, we added an
OVER()
clause after the COUNT(*)
and placed a list of columns, which we checked for duplicate values, after a partition by clause. The partition by clause split rows into groups.Different from using the
GROUP BY
above, the analytic function preserves the result set, therefore, you still can see all the rows in the table once.Because you can use the analytic function in the
WHERE
or HAVING
clause, you need to use the WITH
clause:Or you need to use an inline view:
Now, you should know how to how to find duplicate records in Oracle Database. It’s time to clean up your data by removing the duplicate records.
Delete Duplicate Record in Oracle
Deleting Duplicate Records , if all column values are repeated,
Suppose
Create table called Sports
SQL>create table sports(ID number(2),name varchar2(20),country char(2));
Insert records into Sports table
SQL> insert into sports values(2,'cricket','UK');
SQL> insert into sports values(3,'Hand FootBall','US');
SQL> insert into sports values(4,'Base Ball','US');
SQL> insert into sports values(3,'Hand FootBall','US');
SQL> insert into sports values(4,'Base Ball','US');
Display Records
SQL> Select * from Sports
ID NAME Co
-- -------------------- --
1 cricket IN
2 cricket UK
3 Hand FootBall US
4 Base Ball US
-- -------------------- --
1 cricket IN
2 cricket UK
3 Hand FootBall US
4 Base Ball US
Oracle Sql Delete From Query
Re-insert same values into Sports table
4 rows created.
Display Records again
SQL> Select * from sports;
ID NAME CO
-- -------------------- --
1 cricket IN
2 cricket UK
3 Hand FootBall US
4 Base Ball US
1 cricket IN
2 cricket UK
3 Hand FootBall US
4 Base Ball US
8 rows selected.
-- -------------------- --
1 cricket IN
2 cricket UK
3 Hand FootBall US
4 Base Ball US
1 cricket IN
2 cricket UK
3 Hand FootBall US
4 Base Ball US
8 rows selected.
How To Remove Duplicates In Oracle
Deleting Duplicate Records from Sports Table.
SQL>delete from sports where rowid in (select max(rowid) from sports group by id);
Display Records again, it has all unique rows,
SQL> Select * from Sports
How To Delete Duplicates In Oracle
ID NAME Co
-- -------------------- --
1 cricket IN
2 cricket UK
3 Hand FootBall US
4 Base Ball US
-- -------------------- --
1 cricket IN
2 cricket UK
3 Hand FootBall US
4 Base Ball US
Delete Rows From Oracle Table
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