ORACLE_DELETE

最新推荐文章于 2025-08-21 23:21:52 发布

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最新推荐文章于 2025-08-21 23:21:52 发布

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文章标签：数据库

原文链接：http://www.cnblogs.com/yjhlsbnf/p/7764476.html

本文详细介绍了 SQL 中的 DELETE 语句用法及其注意事项，包括如何从表中删除现有记录而不删除表本身，以及如何避免误删所有记录。通过示例展示了如何使用 WHERE 子句来指定要删除的特定记录。

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SQL DELETE Statement

The SQL DELETE Statement

The DELETE statement is used to delete existing records in a table.

DELETE Syntax

DELETE FROM table_name
WHERE condition;

Note: Be careful when deleting records in a table! Notice the WHERE clause in the DELETE statement. The WHERE clause specifies which record(s) that should be deleted. If you omit the WHERE clause, all records in the table will be deleted!

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

SQL DELETE Example

The following SQL statement deletes the customer "Alfreds Futterkiste" from the "Customers" table:

Example

DELETE FROM Customers
WHERE CustomerName='Alfreds Futterkiste';

The "Customers" table will now look like this:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

Delete All Records

It is possible to delete all rows in a table without deleting the table. This means that the table structure, attributes, and indexes will be intact:

DELETE FROM table_name;

or:

DELETE * FROM table_name;

Delete All Null Records

delete * from emp where comm is null;

delect * from emp where comm='';

CREATE OR REPLACE PROCEDURE emp01_delete_null AS
BEGIN
       DELETE  FROM emp01 WHERE comm IS NULL;
       COMMIT;
END emp01_delete_null;

execute emp01_delete_null;

转载于:https://www.cnblogs.com/yjhlsbnf/p/7764476.html