Nick Kline

TSQL2 language specification

This docuinent specifies a temporal extension to the SQL-92 language standard. The language is designated TSQLZ. The document is organized as follows. The next section indicates the starting point of the design, the SQL92 language. Section 4 lists the desired features on which the TSQL2 Language Design Committee reached consensus. Section 5 presents the major concepts underlying TSQL2. Compatibility with SQL-92 is the topic of Section 6. Section 7 briefly discusses how the language can be implemented. Subsequent sections specify the syntax of the language extensions.

Computing temporal aggregates

Aggregate computation, such as selecting the minimum attribute value of a relation, is expensive, especially in a temporal database. We describe the basic techniques behind computing aggregates in conventional databases and show that these techniques are not efficient when applied to temporal databases. We examine the problem of computing constant intervals (intervals of time for which the aggregate value is constant) used for temporal grouping. We introduce two new algorithms for computing temporal aggregates: the aggregation tree and the k-ordered aggregation tree. An empirical comparison demonstrates that the choice of algorithm depends in part on the amount of memory available, the number of tuples in the underlying relation, and the degree to which the tuples are ordered. This study shows that the simplest strategy is to first sort the underlying relation, then apply the k-ordered aggregation tree algorithm with k=1.<<ETX>>

A TSQL2 tutorial

This tutorial presents the primary constructs of the consensus temporal query language TSQL2 via a media planning scenario. Media planning is a series of decisions involved in the delivery of a promotional message via mass media. We will follow the planning of a particular advertising campaign. We introduce the scenario by identifying the marketing objective. The media plan involves placing commercials, and is recorded in a temporal database. The media plan must then be evaluated; we show how TSQL2 can be used to derive information from the stored data. We then give examples that illustrate storing and querying indeterminate information, comparing multiple versions of the media plan, accommodating changes to the schema, and vacuuming a temporal database of old data.

A Second Example

This chapter expresses the schema and some of the queries of the extensive consensus test suite for temporal relational query languages [Jensen 1993]. The test suite is not related to performance issues, but has a semantic focus and is intended to be an aid in evaluating the user-friendliness of temporal query languages. An attempt is made to express the schema and queries in TSQL2 in a convenient and natural fashion, as an informal evaluation of that language’s user-friendliness.

SQL-92 Compatibility Issues

This chapter will consider compatibility of TSQL2 and SQL-92. Some of the changes in TSQL2 provide more functionality, while others provide space savings, reducing the amount of storage required for time, tamps Through the use of a predefined, default calendar, SQL92, full upward compatibility with SQL-92 is ensured.