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  • OracleL

    DDL  :
    Data Definition Language (DDL) statements are used to define the database structure or schema. Some examples:

    CREATE - to create objects in the database

    ALTER - alters the structure of the database

    DROP - delete objects from the database

    TRUNCATE - remove all records from a table, including all spaces allocated for the records are removed

    COMMENT - add comments to the data dictionary

    RENAME - rename an object

    DML:

    Data Manipulation Language (DML) statements are used for managing data within schema objects. Some examples:

    SELECT - retrieve data from the a database

    INSERT - insert data into a table

    UPDATE - updates existing data within a table

    DELETE - deletes all records from a table, the space for the records remain

    MERGE - UPSERT operation (insert or update)

    CALL - call a PL/SQL or Java subprogram

    EXPLAIN PLAN - explain access path to data

    LOCK TABLE - control concurrency

    DCL

    Data Control Language (DCL) statements. Some examples:

    GRANT - gives user's access privileges to database

    REVOKE - withdraw access privileges given with the GRANT command

    TCL

    Transaction Control (TCL) statements are used to manage the changes made by DML statements. It allows statements to be grouped together into logical transactions.

    COMMIT - save work done

    SAVEPOINT - identify a point in a transaction to which you can later roll back

    ROLLBACK - restore database to original since the last COMMIT

    SET TRANSACTION - Change transaction options like isolation level and what rollback segment to use

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  • 原文地址:https://www.cnblogs.com/ruiy/p/SQL.html
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