noviembre 30, 2022 5:41 pm Published by Leave your thoughts

DDL is also used to specify additional properties of the data. The storage structure and access methods used by the database system by a set of statements in a special type of DDL called a data storage and definition language. These statements define the implementation details of the database schema, which are usually hidden from the users. The data values stored in the database must satisfy certain consistency constraints. For example, suppose the university requires that the account balance of a department must never be negative.

It is the component of the SQL statement that controls access to data and to the database. Basically, DCL statements are grouped with DML statements. Data Definition Language(DDL) is used for describing data and its relationship in a database. The commands only affect the database structure and not the data. It is a database language that allows you to manage and retrieve data from relational databases. All relational database management systems(RDBMS) like SQL Server, MySQL, Oracle, Sybase, Postgres, MS-Access use SQL as their standard database language.

What is Data Definition Language (DDL)?

The alter command modifies any existing table in a database. The Alter command can add up an additional column, drop the existing columns and even change the data types of various columns involved in a DB table. It is mainly used to modify and establish the structure of the objects present in a database by dealing with the database schema descriptions. The SQL commands that can be used to describe the database structure are collectively known as Data Definition Language. It simply works with database schema descriptions and is used to create and modify the database’s database object structure.

Data Definition Language

This lesson has identified data definition language (DDL), a term used to cover SQL statements that update and/or manipulate a database structure. These commands include CREATE, DROP, and ALTER, and are used to add/drop tables, views, indexes, and triggers. DDL statements can be used to add constraints, such as primary or foreign keys to tables. It’s important to have good naming conventions when creating these so that database maintenance is manageable.


So, in the example mentioned above, we are trying to specify the data type using the string CHAR. The database server examines the chosen clause, which is the first and one of the last clauses of the select statement. The reason for this is that we need to know all of the alternative columns basis sql that could be included in the final result set before we can decide what to include in it. When creating a table, the data types most often used include strings (VARCHAR or CHAR); numbers (NUMBER or INTEGER); and dates (DATE). Other commonly used commands include RENAME and COMMENT.

Data Definition Language

These constraints are used to enforce uniqueness, referential or domain integrity.

A data definition language (DDL) is a computer language used to create and modify the structure of database objects in a database. These database objects include views, schemas, tables, indexes, etc. DDL is a standardized language with commands to define the storage groups (stogroups), different structures and objects in a database.

Data Definition Language

DDL statements create, modify and remove database objects, such as tables, indexes and stogroups. DDL is also used in a generic sense to refer to any language that describes data. Data Definition Language (DDL) is used to create and modify the structure of objects in a database using predefined commands and a specific syntax. These database objects include tables, sequences, locations, aliases, schemas and indexes.

Data Definition Language

These commands are used to make modifications to database objects, such as indexes, locations and stogroups. DDL also includes several DROP commands to delete objects in a database. DROP commands cannot be undone, so once an object is deleted, it cannot be recovered.

  • DDL is short name of Data Definition Language, which deals with
    database schemas and descriptions, of how the data should reside in
    the database.
  • Transaction Control Language (TCL) instructions are used in the database to manage transactions.
  • The above command will modify the ‘Emp_Name’ column to data type VARCHAR2 with size 25.
  • Data Definition Language(DDL) is used for describing data and its relationship in a database.
  • TCL allows you to combine your statements into logical transactions.
  • The most notable one is setting permissions for database users, which is done chiefly through the GRANT, REVOKE, and DENY commands.

To learn more about these commands, you can read the SQL INSERT, SQL UPDATE, SQL DELETE – Oh My! Article or take the How to INSERT, UPDATE, and DELETE Data in SQL course right here on LearnSQL.com. The TRUNCATE statement is used to delete all data from a table. TCL is used to run the changes made by the DML statement. Example –We need to create a table for storing Student information of a particular College.

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