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  • ORACLE_DELETE

    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:

    CustomerIDCustomerNameContactNameAddressCityPostalCodeCountry
    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:

    CustomerIDCustomerNameContactNameAddressCityPostalCodeCountry
    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;
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  • 原文地址:https://www.cnblogs.com/yjhlsbnf/p/7764476.html
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