zoukankan      html  css  js  c++  java
  • What are the difference between DDL, DML and DCL commands?

     

    DDL is Data Definition Language statements. 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
    • GRANT - gives user's access privileges to database
    • REVOKE - withdraw access privileges given with the GRANT command

    DML is Data Manipulation Language statements. 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
    • CALL - call a PL/SQL or Java subprogram
    • EXPLAIN PLAN - explain access path to data
    • LOCK TABLE - control concurrency

    DCL is Data Control Language statements. Some examples:

    • 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 what rollback segment to use
  • 相关阅读:
    LibreOJ #507. 「LibreOJ NOI Round #1」接竹竿
    BZOJ 4590: [Shoi2015]自动刷题机
    luogu P3808 【模板】AC自动机(简单版)
    cogs 2569. [東方] 博丽灵梦 梦想妙珠
    codeforces 1C. Ancient Berland Circus
    BZOJ 4570: [Scoi2016]妖怪
    HDU 1392 Surround the Trees
    cogs 999. [東方S2]雾雨魔理沙
    Uva 10652 Board Wrapping
    AC日记——[Sdoi2008]Cave 洞穴勘测 bzoj 2049
  • 原文地址:https://www.cnblogs.com/amadeuslee/p/3744415.html
Copyright © 2011-2022 走看看