Joining Tables

Joins let you construct queries that retrieve data from more than one table.

• Cross Product Joins
  A cross product join returns a result set that produces all possible combinations of rows from the two tables. The number of rows in the result set is the product of the number of rows in the first table and the number of rows in the second table.
• Restricting Joins
  Adding conditions to a query restricts the result set to records that meet specific criteria. Join conditions use comparison operators to eliminate rows from the cross-product result.
• Table Relationships
  Understanding how one table is related to another lets you construct different types of joins.
• Join Operators
  Joins are used to query two or more tables based on the relationship between columns in these tables.
• Using Ad Hoc Joins vs. Join Indexes
  A join index is an internal structure that defines a relationship between the columns in two or more tables. Ad hoc joins are joins that do not use join indexes.
• Joins and Data Types
  Understanding Sybase IQ handles join column data types can help you write more efficient queries.
• Join Support Between Stores or Databases
  Any join within a given Sybase IQ database are supported. This means that you can join any system or user table in the IQ catalog store with any table in the IQ main store, in any order.
• Querying Remote and Heterogeneous Databases
  Component Integration Services (CIS) let you query remote databases and nonrelational data sources. CIS is installed as part of Sybase IQ.
• Joins and Subqueries
  A subquery appears in the main query's SELECT, FROM, WHERE or HAVING clause, and allows you to select rows from one table according to specifications obtained from another table.