Search results
Results from the WOW.Com Content Network
With C or C++ UDF libraries that run in process, the functions are typically registered as built-in functions within the database server and called like any other built-in function in a SQL statement. Running in process allows the function to have full access to the database server's memory, parallelism and processing management capabilities ...
A function is a subprogram written to perform certain computations. A scalar function returns only one value (or NULL), whereas a table function returns a (relational) table comprising zero or more rows, each row with one or more columns. Functions must return a value (using the RETURN keyword), but for stored procedures this is not mandatory.
As the load phase interacts with a database, the constraints defined in the database schema – as well as in triggers activated upon data load – apply (for example, uniqueness, referential integrity, mandatory fields), which also contribute to the overall data quality performance of the ETL process.
The most popular database model for general-purpose databases is the relational model, or more precisely, the relational model as represented by the SQL language. The process of creating a logical database design using this model uses a methodical approach known as normalization. The goal of normalization is to ensure that each elementary "fact ...
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
The derived table also is referred to as an inline view or a select in from list. In the following example, the SQL statement involves a join from the initial Books table to the derived table "Sales". This derived table captures associated book sales information using the ISBN to join to the Books table.
Database-level triggers can help enforce multi-table constraints, or emulate materialized views. If an exception is raised in a TRANSACTION COMMIT trigger, the changes made by the trigger so far are rolled back and the client application is notified, but the transaction remains active as if COMMIT had never been requested; the client ...
For example, instead of using commands such as insert, delete, and update to access a specific table in a database, a class and a few stored procedures could be created in the database. The procedures would be called from a method inside the class, which would return an object containing the requested values.