KNOWLEDGE BASE

Joining Two Identical Custom SQL Statements Produces no Results in the Second Table


Published: 26 Jun 2020
Last Modified Date: 30 Jun 2020

Issue

When connecting to Amazon Redshift data using the Postgres connector, a custom SQL statement joined to an identical custom SQL statement will result in only null values for all fields in the right side of the join.

Environment

  • Tableau Desktop 2020.2.0
  • Amazon Redshift connection using the PostgreSQL connector

Resolution

Option 1
Use the native Redshift connector for the data connection

Option 2
Give the join fields different aliases in the SQL statements

Option 3
Combine the two custom SQL statements into a single statement that also includes the join

Cause

This issue may be related to the driver used since it does not occur when Amazon Redshift connector is used instead of Postgres connector.
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