DDL (Data Definition Language) refers to the CREATE, ALTER and DROP statements
DDL allows to add / modify / delete the logical structures which contain the data or which allow users to access / maintain the data (databases, tables, keys, views…). DDL is about “metadata”.
DML (Data Manipulation Language) refers to the INSERT, UPDATE and DELETE statements
DML allows to add / modify / delete data itself.
DQL (Data Query Language) refers to the SELECT, SHOW and HELP statements (queries)
SELECT is the main DQL instruction. It retrieves data you need. SHOW retrieves infos about the metadata. HELP… is for people who need help.
DCL (Data Control Language) refers to the GRANT and REVOKE statements
DCL is used to grant / revoke permissions on databases and their contents. DCL is simple, but MySQL’s permissions are rather complex. DCL is about security.
DTL (Data Transaction Language) refers to the START TRANSACTION, SAVEPOINT, COMMIT and ROLLBACK [TO SAVEPOINT] statements
DTL is used to manage transactions (operations which include more instructions none of which can be executed if one of them fails).
DDL（数据定义语言）是指CREATE，ALTER和DROP语句
DDL允许添加/修改/删除包含数据的逻辑结构，或允许用户访问/维护数据（数据库，表，键，视图......）的逻辑结构。DDL是关于“元数据”的。
DML（数据操作语言）是指INSERT，UPDATE和DELETE语句
DML允许自己添加/修改/删除数据。
DQL（数据查询语言）是指SELECT，SHOW和HELP语句（查询）
SELECT是主要的DQL指令。它会检索您需要的数据。SHOW检索有关元数据的信息。HELP...适合需要帮助的人。
DCL（数据控制语言）是指GRANT和REVOKE语句
DCL用于授予/撤消对数据库及其内容的权限。DCL很简单，但MySQL的权限相当复杂。DCL是关于安全性的。
DTL（数据事务语言）是指START TRANSACTION，SAVEPOINT，COMMIT和ROLLBACK [TO SAVEPOINT]语句
DTL用于管理事务（包含更多指令的操作，如果其中一个指令失败，则不能执行这些指令）。
月亮永远比树梢看的远：
1、单身程序员：关注公众号【小诚信驿站】，添加我微信 备注 单身_公司_姓名
2、找工作、跳槽程序员：关注公众号【小诚信驿站】，添加我微信 备注 内推_公司_姓名
3、程序员交流招聘，添加扣扣群：300458205