Category Archives: RDBMS concepts

Derived tables

A derived table is defined by the evaluation of a query expression and differs from a regular table in that it is neither described in system catalogs nor stored on disk. In Adaptive Server, a derived table may be a … Continue reading

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Computed columns

Computed columns were introduced in Sybase ASE 15 to provide easier data manipulation and faster data access. Computed columns are columns that are defined by an expression. This expression can be built by combining regular columns in the same row … Continue reading

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Identity column

An IDENTITY column contains a value for each row, generated automatically by Adaptive Server, that uniquely identifies the row within the table. Each table can have only one IDENTITY column. You can define an IDENTITY column when you create a … Continue reading

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Query Processor

Query processor processes SQL queries specified by user. The processor yields highly efficient query plans that execute using minimal resources, and ensure that results are consistent and correct. To process a query efficiently, the query processor uses: SQL Query specified by user. … Continue reading

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Local and global indexes on partitioned tables

Indexes, like tables, can be partitioned. Prior to Adaptive Server 15.0, all indexes were global. With Adaptive Server 15.0, you can create local as well as global indexes. Adaptive Server supports local and global indexes. A local index – spans … Continue reading

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Partitioning Strategies

Data partitioning breaks up large tables and indexes into smaller pieces that can reside on separate partitions. Note: A segment is a portion of a device that is defined within ASE. It is used for the storage of specific types … Continue reading

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Scrollable Cursors

Adaptive Server Enterprise allows both scrollable and nonscrollable cursors, which can be either semi‐sensitive or insensitive. “Scrollable” means that you can scroll through the cursor result set by fetching any, or many, rows, rather than one row at a time; … Continue reading

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Denormalization

In a relational database, denormalization is an approach to speeding up read performance (data retrieval) in which the administrator selectively adds back specific instances of redundant data after the data structure has been normalized. A denormalised data model is not … Continue reading

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Normalization

Normalization is the process of efficiently organizing data in a database. There are two goals of the normalization process: eliminating redundant data (for example, storing the same data in more than one table) and ensuring data dependencies make sense (only … Continue reading

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