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In the context of SQL, data definition or data description language (DDL) is a syntax for creating and modifying database objects such as tables, indices, and users. DDL statements are similar to a computer programming language for defining data structures , especially database schemas .
A check constraint is a type of integrity constraint in SQL which specifies a requirement that must be met by each row in a database table. The constraint must be a predicate . It can refer to a single column, or multiple columns of the table.
The term "schema" refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases). The formal definition of a database schema is a set of formulas (sentences) called integrity constraints imposed on a database.
Oracle Forms is a software product for creating screens that interact with an Oracle database.It has an IDE that includes an object navigator, property sheet, and code editor that uses PL/SQL.
A database management system, in its access control mechanism, can also apply mandatory access control; in this case, the objects are tables, views, procedures, etc. In mandatory access control, the security policy is centrally controlled by a policy administrator and is guaranteed (in principle) to be enforced for all users.
Tables are linked using primary key to foreign key relationships. It is possible for users to update one table in a relationship in such a way that the relationship is no longer consistent and this is known as breaking referential integrity. An example of breaking referential integrity: if a table of employees includes a department number for ...
Durability against failures that occur at transaction level, such as canceled calls and inconsistent actions that may be blocked before committing by constraints and triggers, is guaranteed by the serializability property of the execution of transactions. The state generated by the effects of precedently committed transactions is available in ...
The advantages of using a natural key to uniquely identify records in a relation include less disk space usage, the natural key is an attribute that is related to the business or the real world so in most cases, it is already being stored in the relation which saves disk space as compared to creating a new column for storing the surrogate key.