Core Concepts Discussion Question 4-5
Database management system (DBMS) allows users to create their own databases using data definition languages (DDLs) and manipulate file data using data manipulation language (DMLs). In accordance with the text, “DDLs of DBMSs that enable users to define the record structure of any particular database table tab the individual fields that each record will contain; thus, DDL is the language of DBMS used to create the data dictionaries”(Simkin, Norman, & Rose, 2012).
DDL is the schema or structure of the database examples are: “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” (Oracle, 2012).
DML statements are used for managing data within schema objects examples are “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” (Oracle, 2004).
Oracle. (Aug. 4, 2004).What are the difference between DDL, DML and DCL commands? http://www.orafaq.com/faq/what_are_the_difference_between_ddl_dml_and_dcl_commands
Simkin, Mark, Norman, Carolyn, & Rose, Jacob. (November 2012). Core Concepts of Accounting Information Systems. 12th edition. John Wiley & Sons, Inc.
Data Definition Language (DDL) is a standard for commands that define the different structures in a database. DDL statements create, modify, and remove database objects such as tables, indexes, and users. Common DDL statements are CREATE, ALTER, and DROP.
I agree. DDL is used to create and destroy databases and database objects. These commands will primarily be used by database administrators. The DDLs allows consistency constraints to be specified and support authorization, giving different access rights to different users, and focus on specifying types of attributes of relations. According to Whitehorn, “SQL language that splits neatly into two parts. There is the data definition language (DDL) section and the data manipulation language (DML)section." The DDL section is used for creating database objects, such as tables. The DML section is used to manipulate the data such as querying it.
Whitehorn, Mike. University of Dundee. The difference between data definition language (DDL) and data manipulation language (DML). http://searchdatamanagement.techtarget.com/answer/The-difference-between-data-definition-language-DDL-and-data-manipulation-language-DML
Data Definition Language (DDL) statements vary tremendously among DBMSs data definition operations: creating and dropping tables, indexes, and views; altering tables; and granting and revoking privileges.
I agree. “a database scheme is specified by a set of definition which are expressed by a special language DDL, result of compilation of DDL statement is a set of tables which are stored in a special file called Data Dictionary, and then DDL defines the structure of data, which DDL statements in SQL language are responsible for creating or modifying database structures such as tables, views, and indexes” (Dotnetguts, 2007). This allows the specification of not only a set of relations but also information about each relation, the schema for each relation, the domain of values associated with each attribute, integrity constraints, the set of indices to be maintained for each relations, security and authorization information for each relation, and the physical storage structure of each relation on disk.
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