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DDL generation for target DBMS from object definition, either for the entire database or for individual objects such as tables, views, columns and relations. Type-safe API for dynamic SQL command generation allows dynamic building of SQL statements using API methods and object references only instead of string literals.
Indexes are useful for many applications but come with some limitations. Consider the following SQL statement: SELECT first_name FROM people WHERE last_name = 'Smith';. To process this statement without an index the database software must look at the last_name column on every row in the table (this is known as a full table scan).
Some graphical data mapping tools allow users to "auto-connect" a source and a destination. This feature is dependent on the source and destination data element name being the same. Transformation programs are automatically created in SQL, XSLT, Java, or C++.
[citation needed] For this reason, many programmers find themselves more at home with an object-SQL mapping system, even though most object-oriented databases are able to process SQL queries to a limited extent. Other OODBMS provide replication to SQL databases, as a means of addressing the need for ad-hoc queries, while preserving well-known ...
A query includes a list of columns to include in the final result, normally immediately following the SELECT keyword. An asterisk ("*") can be used to specify that the query should return all columns of the queried tables. SELECT is the most complex statement in SQL, with optional keywords and clauses that include:
The terms schema matching and mapping are often used interchangeably for a database process. For this article, we differentiate the two as follows: schema matching is the process of identifying that two objects are semantically related (scope of this article) while mapping refers to the transformations between the objects.
Most relational databases use the SQL data definition and query language; these systems implement what can be regarded as an engineering approximation to the relational model. A table in a SQL database schema corresponds to a predicate variable; the contents of a table to a relation; key constraints, other constraints, and SQL queries ...
Tabular data is two dimensional — data is modeled as rows and columns. However, computer systems represent data in a linear memory model, both in-disk and in-memory. [7] [8] [9] Therefore, a table in a linear memory model requires mapping its two-dimensional scheme into a one-dimensional space. Data orientation is to the decision taken in ...