Removing records

To remove records from the table, the Delete operator is applied:

Delete from nameTablitsa WHERE CONDITION;

This operator removes the record from the specified table (and not separate column values) that satisfy the specified condition. The condition is a logical expression, the various designs of which were considered in previous laboratory classes.

The following query deletes the record from the Customer table, in which the value of the LNAME column is "Ivanov":

Delete from Customer.

Where Lname \u003d "Ivanov"

If the table contains information about several clients with the surname of Ivanov, then all of them will be removed.

In the WHERE statement, it may be a subquering to a data sample (SELECT statement). Subqueries in the Delete operator work in the same way as in the SELECT statement. The following request deletes all customers from the city of Moscow, while the unique city identifier is returned using the subquery.

Delete from Customer.

WHERE IDCITY IN (SELECT IDCITY FROM CITY WHERE CITYNAME \u003d "MOSCOW")

Transact-SQL extends a standard SQL, allowing you to use in the DELETE statement another from one. This extension in which the connection is set can be used instead of an invested query in the WHERE clause to specify the removable lines. It allows you to specify the data from the second from and delete the corresponding lines from the table in the first offer From. In particular, the previous request may be rewritten as follows.

Delete from Customer.

From Customer K Inner Join

The operation of removing records from the table is dangerous in the sense, which is associated with the risk of irreversible data loss in the case of semantic (but not syntactic) errors in the wording of SQL expression. To avoid trouble, it is recommended to first execute the appropriate selection request to view which records will be deleted. For example, before performing the previously considered, the deletion request will not prevent the appropriate selection request.

SELECT *

From Customer K Inner Join

CITY C ON K.IDCITY \u003d C.IDCITY AND C.CityName \u003d "Moscow"

To delete all records from the table, it is enough to use the Delete statement without the key word WHERE. At the same time, the table with all the columns defined in it remains and is ready to insert new records. For example, the next request deletes records of all goods.

Delete from Product

Task for independent work: Formulate in SQL language Request for removing all orders that do not have any product (i.e. all empty orders).

Removing repetitive lines from the table in Oracle (14)

Solution 1)

Delete from Emp Where Rowid Not In (Select Max (Rowid) from Emp Group by Empno);

Solution 2)

Delete from Emp Where Rowid Rowid Rid, Row_Number by Empno) RN from Emp) WHERE RN\u003e 1);

Solution 3)

I test something in Oracle and fill the table with some examples of data, but in the process I accidentally loaded the duplicates of the records, so now I can't create a primary key using some of the columns.

How to delete all repetitive lines and leave only one of them?

For better performance, that's what I wrote:
(see execution plan)

Delete from Your_Table Where Rowid In (Select T1.rowid from Your_Table T1 Left Outer Join (Select Min (Rowid) As Rowid, Column1, Column2, Column3 From Your_Table Group by Column1, Column2, Column3) CO1 ON (T1.ROWID \u003d CO1. ROWID) WHERE CO1.ROWID IS NULL);

Check below the scripts -

CREATE TABLE TEST (ID INT, SAL INT);

INSERT INTO TEST VALUES (1,100); INSERT INTO TEST VALUES (1,100); INSERT INTO TEST VALUES (2,200); INSERT INTO TEST VALUES (2,200); INSERT INTO TEST VALUES (3,300); INSERT INTO TEST VALUES (3,300); COMMIT;

SELECT * FROM TEST;

You will see here 6 records.
4.Run below the query -

Delete From Test Where Rowid In (Select Rowid from (Select Rowid Row_number () Over (Partition by ID Order by Sal) DUP FROM TEST) WHERE DUP\u003e 1)

1. sELECT * FROM TEST;

You will see that the duplicates of the records were removed.
I hope this solves your request. Thanks :)

To select duplicates, only the request format can be:

Select GroupFunction (Column1), GroupFunction (Column2), ..., Count (Column1), Column1, Column2 ... from our_table group by Column1, Column2, Column3 ... Having Count (column1)\u003e 1

Thus, the correct request on another suggestion:

Delete from Tablename A Where a.rowid\u003e Any (Select B.rowid from Tablename B Where A.FieldName \u003d B.FieldName and a.fieldname2 \u003d B.FieldName2 And .... So on .. to Identify the duplicate Rows .. ..)

This query will save the oldest record in the database for the criteria selected in the WHERE CLAUSE.

Oracle Certified Associate (2008)

I have not seen the answers that use general table expressions and window functions. This is what makes it easier for me to work.

DELETE FROM YourTable WHERE ROWID IN (WITH Duplicates AS (SELECT ROWID RID, ROW_NUMBER () OVER (PARTITION BY First_Name, Last_Name, Birth_Date) AS RN SUM (1) OVER (PARTITION BY First_Name, Last_Name, Birth_Date ORDER BY ROWID ROWS BETWEEN UNBOUNDED PRECEDING And unbounded following) AS CNT from YourTable Where Load_Date Is Null) Select Rid From Duplicates Where Rn\u003e 1);

What should be noted:

1) We check only duplicate fields in the section.

2) If you have a reason to choose one duplicate over others, you can use the ORDER BY offer so that this line may have ROW_NUMBER () \u003d 1

3) You can change the duplicate of the number saved by changing the final offer of WHERE to "WHERE RN\u003e N" with N\u003e \u003d 1 (I thought that n \u003d 0 will delete all rows with duplicates, but simply delete all the lines),

4) Added field section SUM, CTE query, which will marry each FOW line numbers in the group. Therefore, to select rows with duplicates, including the first element, use "WHERE CNT\u003e 1".

1. Demand

Delete from Emp Where Rowid Not In (Select Max (Rowid) from Emp Group by Empno);

2. slotion

Delete from Emp Where Rowid Rowid Rid, Row_Number by Empno) RN from Emp) WHERE RN\u003e 1);

3.Solution

DELETE from EMP E1 WHERE ROWID NOT IN (SELECT MAX (ROWID) from EMP E2 WHERE E1.Empno \u003d E2.Empno);

4. Demand

Delete from Emp Where Rowid Rowid Rid, Dense_rank () Over (Partition by Empno Order by Rowid) RN from EMP) WHERE RN\u003e 1);

CREATE OR REPLACE PROCEDURE DELETE_DUPLICATE_ENQ AS CURSOR C1 IS SELECT * FROM ENQUIRY; begin for z in c1 loop delete enquiry where enquiry.enquiryno \u003d z.ENQUIRYNO AND ROWID\u003e Any (Select Rowid from Enquiry Where Enquiry.enquiryno \u003d z.ENQUIRYNO); End Loop; END DELETE_DUPLICATE_ENQ;

CREATE TABLE ABCD (ID Number (10), Name Varchar2 (20)) INSERT INTO ABCD VALUES (1, "ABC") INSERT INTO ABCD VALUES (2, "PQR") INSERT INTO ABCD VALUES (3, "XYZ") INSERT INTO ABCD VALUES (1, "ABC") INSERT INTO ABCD VALUES (2, "PQR") INSERT INTO ABCD VALUES (3, "XYZ") SELECT * FROM ABCD ID NAME 1 ABC 2 PQR 3 XYZ 1 ABC 2 PQR 3 XYZ Delete Duplicate Record But Keep Distinct Record In Table Delete from ABCD A WHERE ROWID\u003e (SELECT MIN (ROWID) from ABCD B WHERE B.ID \u003d A.ID); Run The Above Query 3 Rows Delete Select * from ABCD ID NAME 1 ABC 2 PQR 3 XYZ

removal by Rowid Oracle (14)

I test something in Oracle and fill the table with some examples of data, but in the process I accidentally loaded the duplicates of the records, so now I can't create a primary key using some of the columns.

How to delete all repetitive lines and leave only one of them?

Solution 1)

Delete from Emp Where Rowid Not In (Select Max (Rowid) from Emp Group by Empno);

Solution 2)

Delete from Emp Where Rowid Rowid Rid, Row_Number by Empno) RN from Emp) WHERE RN\u003e 1);

Solution 3)

For better performance, that's what I wrote:
(see execution plan)

Delete from Your_Table Where Rowid In (Select T1.rowid from Your_Table T1 Left Outer Join (Select Min (Rowid) As Rowid, Column1, Column2, Column3 From Your_Table Group by Column1, Column2, Column3) CO1 ON (T1.ROWID \u003d CO1. ROWID) WHERE CO1.ROWID IS NULL);

Check below the scripts -

CREATE TABLE TEST (ID INT, SAL INT);

INSERT INTO TEST VALUES (1,100); INSERT INTO TEST VALUES (1,100); INSERT INTO TEST VALUES (2,200); INSERT INTO TEST VALUES (2,200); INSERT INTO TEST VALUES (3,300); INSERT INTO TEST VALUES (3,300); COMMIT;

SELECT * FROM TEST;

You will see here 6 records.
4.Run below the query -

Delete From Test Where Rowid In (Select Rowid from (Select Rowid Row_number () Over (Partition by ID Order by Sal) DUP FROM TEST) WHERE DUP\u003e 1)

1. sELECT * FROM TEST;

You will see that the duplicates of the records were removed.
I hope this solves your request. Thanks :)

To select duplicates, only the request format can be:

Select GroupFunction (Column1), GroupFunction (Column2), ..., Count (Column1), Column1, Column2 ... from our_table group by Column1, Column2, Column3 ... Having Count (column1)\u003e 1

Thus, the correct request on another suggestion:

Delete from Tablename A Where a.rowid\u003e Any (Select B.rowid from Tablename B Where A.FieldName \u003d B.FieldName and a.fieldname2 \u003d B.FieldName2 And .... So on .. to Identify the duplicate Rows .. ..)

This query will save the oldest record in the database for the criteria selected in the WHERE CLAUSE.

Oracle Certified Associate (2008)

I have not seen the answers that use general table expressions and window functions. This is what makes it easier for me to work.

DELETE FROM YourTable WHERE ROWID IN (WITH Duplicates AS (SELECT ROWID RID, ROW_NUMBER () OVER (PARTITION BY First_Name, Last_Name, Birth_Date) AS RN SUM (1) OVER (PARTITION BY First_Name, Last_Name, Birth_Date ORDER BY ROWID ROWS BETWEEN UNBOUNDED PRECEDING And unbounded following) AS CNT from YourTable Where Load_Date Is Null) Select Rid From Duplicates Where Rn\u003e 1);

What should be noted:

1) We check only duplicate fields in the section.

2) If you have a reason to choose one duplicate over others, you can use the ORDER BY offer so that this line may have ROW_NUMBER () \u003d 1

3) You can change the duplicate of the number saved by changing the final offer of WHERE to "WHERE RN\u003e N" with N\u003e \u003d 1 (I thought that n \u003d 0 will delete all rows with duplicates, but simply delete all the lines),

4) Added field section SUM, CTE query, which will marry each FOW line numbers in the group. Therefore, to select rows with duplicates, including the first element, use "WHERE CNT\u003e 1".

1. Demand

Delete from Emp Where Rowid Not In (Select Max (Rowid) from Emp Group by Empno);

2. slotion

Delete from Emp Where Rowid Rowid Rid, Row_Number by Empno) RN from Emp) WHERE RN\u003e 1);

3.Solution

DELETE from EMP E1 WHERE ROWID NOT IN (SELECT MAX (ROWID) from EMP E2 WHERE E1.Empno \u003d E2.Empno);

4. Demand

Delete from Emp Where Rowid Rowid Rid, Dense_rank () Over (Partition by Empno Order by Rowid) RN from EMP) WHERE RN\u003e 1);

CREATE OR REPLACE PROCEDURE DELETE_DUPLICATE_ENQ AS CURSOR C1 IS SELECT * FROM ENQUIRY; begin for z in c1 loop delete enquiry where enquiry.enquiryno \u003d z.ENQUIRYNO AND ROWID\u003e Any (Select Rowid from Enquiry Where Enquiry.enquiryno \u003d z.ENQUIRYNO); End Loop; END DELETE_DUPLICATE_ENQ;

CREATE TABLE ABCD (ID Number (10), Name Varchar2 (20)) INSERT INTO ABCD VALUES (1, "ABC") INSERT INTO ABCD VALUES (2, "PQR") INSERT INTO ABCD VALUES (3, "XYZ") INSERT INTO ABCD VALUES (1, "ABC") INSERT INTO ABCD VALUES (2, "PQR") INSERT INTO ABCD VALUES (3, "XYZ") SELECT * FROM ABCD ID NAME 1 ABC 2 PQR 3 XYZ 1 ABC 2 PQR 3 XYZ Delete Duplicate Record But Keep Distinct Record In Table Delete from ABCD A WHERE ROWID\u003e (SELECT MIN (ROWID) from ABCD B WHERE B.ID \u003d A.ID); Run The Above Query 3 Rows Delete Select * from ABCD ID NAME 1 ABC 2 PQR 3 XYZ

Oracle allows you to delete lines from tables, views, materialized representations, subqueries and partitioned views and tables as follows.

(NameTables | only (Name_Table)) [Pseudonym] [(Partition) Subpartition

(name)))] | (subquery)]) | Table (expression_lit_collection) [(+)])

INTO variable [, ...]]

The parameters are shown below.

name_Table [pseudonym]

Specifies the table, representation, materialized view or partitioned table or view, from where the records will be deleted. If you wish, you can in front of the name_Table specify the scheme or specify after the name of the table connection to the database. Otherwise, the Oracle system will use the current diagram and local database server. If you wish, you can assign some pseudonym name. The pseudonym is necessary if the table refers to the attribute or object type method.

Partition Name section

The deletion operation applies to the specified partition, and not to the entire table. When you delete from a partitioned table, it is not necessary to specify the name of the partition, but this in many cases helps to reduce the complexity of the offer of the WHERE.

Subpartition)

Removal applies to the specified subsection, and not to the entire table.

(subquery)])

It is indicated that the purpose of the removal operation is nested subquery, and not a table, representation or other database object. The parameters of this proposal are as follows.

subquery

The SELECT statement is specified, which is a subquery. You can create any standard subquery, but it cannot contain ORDER BY offers.

With Read Only

It is indicated that the subquery cannot be updated.

WITH CHECK OPTION

The Oracle system will deflect any changes to the remote table that are not visible in the resulting subquering data set.

Constraint name_name

The Oracle system will limit the changes made by based on the restriction with the name_name name.

Table (expression for rolling) [(+)]

The Oracle system will handle expressions of the diverse as a table, although in fact it can be a subquery, a function or other constructor of the collection. In any case, the value returned by the expression for the rolling should be a nested table or varray.

Returning expression

Rows affected by the command where the Delete command typically returns only the number of remote strings. The RETURNING proposal can be used if the goal of the command is a table, a materialized view or representation by one base table. If the offer is used when deleting a single line, then the values \u200b\u200bfrom the remote string, which are defined by the expression are stored in PL / SQL variables and bind variables (Bind Variables). If the proposal is used when removing many lines, then the values \u200b\u200bfrom remote strings that are determined by the agricultural & m are stored in bind arrays (Bind Arrays).

Into variable

Specify the variables in which the values \u200b\u200breturned as a result of the proposal of the RETURNING.

When executing the Delete Oracle instruction, returns the place back to the table or index where the data was stored in the table (or base table).

If the data is deleted from the presentation, the view cannot contain operations over sets, the Distinct keyword, connections, an aggregate function, analytical function, subqueries SELECT, offers Group BY, offers Order by, offers Connect by or Start Wit.

Below is an example in which we delete data from a remote server.

Delete From Scott. [Email Protected];

In the following example

we delete data from the table specified in the expression for the collection.

DELETE TABLE (Select ContactName from Customers

with WHERE C.CustomerID \u003d "Bottm") s where s. Region is null or s.country \u003d "Mexico";

But an example of deleting from the section.

Delete from Sales Partition (Sales_q3_1997) WHERE QTY\u003e 10000;

Finally, in the following example, we use the RETURNING proposal to see remote values.

Delete from Employee WHERE JOB_ID \u003d 13

And hire_date + to_yminterval ("01-06") \u003d.

In the previous example, entries from the Employee table are deleted, and the values \u200b\u200bof J OBI VL are returned to a predetermined variable: INTOL.