15.10 - Cardinality and Uniqueness Statistics for the Reasonable Unindexed Join Examples - Teradata Database

Teradata Database SQL Request and Transaction Processing

prodname
Teradata Database
vrm_release
15.10
category
Programming Reference
User Guide
featnum
B035-1142-151K

For LT/ST-J2a (Reasonable Unindexed) join example, the following row information is given for the small tables:

 

                         Attribute

                                 Cardinality (rows)

                           color

                                              3

                           size

                                            10

                           options

                                            10

The following statistics information is given for the large table:

 

                   Column Name

                        Number of Unique Values

                           color

                                              6

                           size

                                            30

                           options

                                          300

No index is created on the collection of join columns (color, size, and options) of the large table.

The following query is used for the LT/ST-J2a (Reasonable Unindexed) join in this example:

     SELECT * 
     FROM widget, color, size, options
     WHERE widgets.color=color.code
     AND   widgets.size=size.code
     AND   widgets.options=options.code
     AND   size.description=options.description;