Vertica Analytics Platform Version 9.2.x Documentation

Joined-Table

Specifies how to join tables.

Syntax

table‑reference [join-type] JOIN table-reference[ TABLESAMPLE(sampling‑pct) ] [ ON join‑predicate ] 

Parameters

table‑reference

A table or another joined-table.

join-type

Valid Values:

TABLESAMPLE

Specifies to use simple random sampling to return an approximate percentage of records. All rows in the total potential return set are equally eligible to be included in the sampling. Vertica performs this sampling before other filters in the query are applied. The number of records returned is not guaranteed to be the exact percentage of records defined by sampling‑pct.

The TABLESAMPLE option is valid only with user-defined tables and Data Collector (DC) tables. Views and system tables are not supported.

sampling‑pct Specifies the percentage of records to be returned as a part of sampling. The value must be greater than 0 and less than 100.
ON join‑predicate

An equi-join based on one or more columns in the joined tables. invalid for NATURAL and CROSS joins, required for all other join types.

Alternative JOIN Syntax Options

Vertica supports two older join syntax conventions:

  • Table joins specified by join predicate in a WHERE clause
  • Table joins specified by a USING clause

For details, see Join Syntax in Analyzing Data.

Examples

The following SELECT statement qualifies its JOIN clause with the TABLESAMPLE option:

=> SELECT user_id.id, user_name.name FROM user_name TABLESAMPLE(50)
     JOIN user_id TABLESAMPLE(50) ON user_name.id = user_id.id;
  id  |  name
------+--------
  489 | Markus
 2234 | Cato
  763 | Pompey
(3 rows)