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Querying Data

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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 GPORCA
    In Greenplum Database, the default GPORCA optmizer co-exists with the legacy query optimizer.
  • Defining Queries
    Greenplum Database is based on the PostgreSQL implementation of the SQL standard.
  • WITH Queries (Common Table Expressions)
    The WITH clause of the SELECT command provides a way to write subqueries for use in a larger SELECT query.
  • Using Functions and Operators
    Description of user-defined and built-in functions and operators in Greenplum Database.
  • Working with JSON Data
    Greenplum Database supports the json data type that stores JSON (JavaScript Object Notation) data.
  • Working with XML Data
    Greenplum Database supports the xml data type that stores XML data.
  • 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: Greenplum Database Administrator Guide