Documentation about InterSystems Caché

The Selectivity value for a column is the percentage of rows within a table that would be returned as a result of query searching for a typical value of the column. A measure of distinctness of the data

ExtentSize

ExtentSize is the approximate number of rows in the table. The number does not need to be exact, just relative to the size of other tables. The Query Optimizer uses ExtentSize to find the starting table for queries.

TuneTable

TuneTable does the same job like UPDATE STATISTICS in MS SQL Server. During its evaluation of a query, the query optimizer uses these statistics to estimate the cost of using an index to satisfy the query. Having good statistics for table cardinality and column cardinalities is very importent.
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Caché JDBC driver

The InterSystems Caché JDBC driver are an type 4 JDBC driver. Here you find information which JDBC driver comes with what version of Intersystems Caché database.
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Programming:SQL

Programming:SQL

From Wikibooks

SQL, which is an acronym for Structured Query Language is a method for specifying the means of either requesting data from a database, of updating data in a database, of adding data to a database, or of manipulating metadata about the database.

SQL

From Wikipedia, the free encyclopedia.

Structured Query Language (SQL) is the most popular computer language used to create, modify and retrieve data from relational database management systems. The language has evolved beyond its original purpose to support object-relational database management systems. It is an ANSI/ISO standard.