问题

I have heard the terms DDL and DML in reference to databases, but I don\'t understand what they are.

What are they and how do they relate to SQL?

回答1:

DDL is Data Definition Language : it is used to define data structures.

For example, with SQL, it would be instructions such as create table, alter table, ...

DML is Data Manipulation Language : it is used to manipulate data itself.

For example, with SQL, it would be instructions such as insert, update, delete, ...

回答2:

More information see here: MySQL What is DDL, DML and DCL?, the original is as follows:

DDL

DDL is short name of Data Definition Language, which deals with database schemas and descriptions, of how the data should reside in the database.

CREATE – to create database and its objects like (table, index, views, store procedure, function and triggers)

ALTER – alters the structure of the existing 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

DML is short name of Data Manipulation Language which deals with data manipulation, and includes most common SQL statements such SELECT, INSERT, UPDATE, DELETE etc, and it is used to store, modify, retrieve, delete and update data in database.

SELECT – retrieve data from the a database

INSERT – insert data into a table

UPDATE – updates existing data within a table

DELETE – Delete all records from a database table

MERGE – UPSERT operation (insert or update)

CALL – call a PL/SQL or Java subprogram

EXPLAIN PLAN – interpretation of the data access path

LOCK TABLE – concurrency Control

DCL

DCL is short name of Data Control Language which includes commands such as GRANT, and mostly concerned with rights, permissions and other controls of the database system.

GRANT – allow users access privileges to database

REVOKE – withdraw users access privileges given by using the GRANT command

TCL

TCL is short name of Transaction Control Language which deals with transaction within a database.

COMMIT – commits a Transaction

ROLLBACK – rollback a transaction in case of any error occurs

SAVEPOINT – to rollback the transaction making points within groups

SET TRANSACTION – specify characteristics for the transaction

回答3:

DDL is Data Definition Language : Specification notation for defining the database schema. It works on Schema level.

DDL commands are:

create,drop,alter,rename

For example:

create table account (
  account-number  char(10),
 balance integer);

DML is Data Manipulation Language .It is used for accessing and manipulating the data.

DML commands are:

select,insert,delete,update,call

For example :

update account set balance = 1000 where account_number = 01;

回答4:

DDL, Data Definition Language

Create and modify the structure of database object in a database.
These database object may have the Table, view, schema, indexes....etc

e.g.:

CREATE, ALTER, DROP, TRUNCATE, COMMIT, etc.

DML, Data Manipulation Language

DML statement are affect on table. So that is the basic operations we perform in a table.

Basic crud operation are perform in table.
These crud operation are perform by the SELECT, INSERT, UPDATE, etc.

Below Commands are used in DML:

INSERT, UPDATE, SELECT, DELETE, etc.

回答5:

In layman terms suppose you want to build a house, what do you do.

DDL i.e Data Definition Language

Build from scratch
Rennovate it
Destroy the older one and recreate it from scratch

that is

CREATE
ALTER
DROP & CREATE

DML i.e. Data Manipulation Language

People come/go inside/from your house

SELECT
DELETE
UPDATE
TRUNCATE

DCL i.e. Data Control Language

You want to control the people what part of the house they are allowed to access and kind of access.

GRANT PERMISSION

回答6:

DML is abbreviation of Data Manipulation Language. It is used to retrieve, store, modify, delete, insert and update data in database.

Examples: SELECT, UPDATE, INSERT statements

DDL is abbreviation of Data Definition Language. It is used to create and modify the structure of database objects in database.

Examples: CREATE, ALTER, DROP statements

Visit this site for more info: http://blog.sqlauthority.com/2008/01/15/sql-server-what-is-dml-ddl-dcl-and-tcl-introduction-and-examples/

回答7:

DDL is Data Definition Language: Just think you are defining the DB. So we use CREATE,ALTER TRUNCATE commands.
DML is after defining we are Manipulating the data. So we use SELECT,INSERT, UPDATE, DELETE command.

Remember DDL commands are auto-committed. You don't need to use COMMIT statements.
DML (Data Manipulation Language) commands need to be commited/rolled back.

回答8:

DDL = Data Definition Language, any commands that provides structure and other information about your data

DML = Data Manipulation Language, there's only 3 of them, INSERT, UPDATE, DELETE. 4, if you will count SELECT * INTO x_tbl from tbl of MSSQL (ANSI SQL: CREATE TABLE x_tbl AS SELECT * FROM tbl)

回答9:

In simple words.

DDL(Data definition language): will work on structure of data. define the data structures.

DML (data manipulation language): will work on data. manipulates the data itself

回答10:

DDL: Change the schema

DML: Change the data

Seems specific to MySQL limitations (rails's source code)

回答11:

DDL

Create,Alter,Drop of (Databases,Tables,Keys,Index,Views,Functions,Stored Procedures)

DML

Insert ,Delete,Update,Truncate of (Tables)

回答12:

DDL stands for Data Definition Language. DDL is used for defining structure of the table such as create a table or adding a column to table and even drop and truncate table. DML stands for Data Manipulation Language. As the name suggest DML used for manipulating the data of table. There are some commands in DML such as insert and delete.

来源：https://stackoverflow.com/questions/2578194/what-is-ddl-and-dml

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sql

ddl

dml

What is DDL and DML? [closed]

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