Querying Data

This topic provides information about using SQL in Greenplum databases.

You enter SQL statements called queries to view, change, and analyze data in a database using the psql interactive SQL client and other client tools.

  • About Greenplum Query Processing
    This topic provides an overview of how Greenplum Database processes queries. Understanding this process can be useful when writing and tuning queries.
  • About the Pivotal Query Optimizer
    In Greenplum Database 4.3.5.0 and later, the Pivotal Query Optimizer co-exists with the legacy query optimizer.
  • Defining Queries
    Greenplum Database is based on the PostgreSQL implementation of the SQL standard.
  • Using Functions and Operators
    Greenplum Database evaluates functions and operators used in SQL expressions. Some functions and operators are only allowed to execute on the master since they could lead to inconsistencies in segment databases.
  • Query Performance
    Greenplum Database dynamically eliminates irrelevant partitions in a table and optimally allocates memory for different operators in a query.
  • Managing Spill Files Generated by Queries
    Greenplum Database creates spill files, also known as workfiles, on disk if it does not have sufficient memory to execute an SQL query in memory.
  • Query Profiling
    Examine the query plans of poorly performing queries to identify possible performance tuning opportunities.
Parent topic: Working with Databases