CData Python Connector for Apache Impala

Build 21.0.7930

SELECT Statements

A SELECT statement can consist of the following basic clauses.

  • SELECT
  • INTO
  • FROM
  • JOIN
  • WHERE
  • GROUP BY
  • HAVING
  • UNION
  • ORDER BY
  • LIMIT

SELECT Syntax

The following syntax diagram outlines the syntax supported by the SQL engine of the provider:

SELECT {
  [ TOP <numeric_literal> | DISTINCT ]
  { 
    * 
    | { 
        <expression> [ [ AS ] <column_reference> ] 
        | { <table_name> | <correlation_name> } .* 
      } [ , ... ] 
  }
  [ INTO csv:// [ filename= ] <file_path> [ ;delimiter=tab ] ]
  { 
    FROM <table_reference> [ [ AS ] <identifier> ] 
  } [ , ... ]
  [ [  
      INNER | { { LEFT | RIGHT | FULL } [ OUTER ] } 
    ] JOIN <table_reference> [ ON <search_condition> ] [ [ AS ] <identifier> ] 
  ] [ ... ] 
  [ WHERE <search_condition> ]
  [ GROUP BY <column_reference> [ , ... ]
  [ HAVING <search_condition> ]
  [ UNION [ ALL ] <select_statement> ]
  [ 
    ORDER BY 
    <column_reference> [ ASC | DESC ] [ NULLS FIRST | NULLS LAST ]
  ]
  [ 
    LIMIT <expression>
    [ 
      { OFFSET | , }
      <expression> 
    ]
  ] 
} | SCOPE_IDENTITY() 

<expression> ::=
  | <column_reference>
  | @ <parameter> 
  | ?
  | COUNT( * | { [ DISTINCT ] <expression> } )
  | { AVG | MAX | MIN | SUM | COUNT } ( <expression> ) 
  | NULLIF ( <expression> , <expression> ) 
  | COALESCE ( <expression> , ... ) 
  | CASE <expression>
      WHEN { <expression> | <search_condition> } THEN { <expression> | NULL } [ ... ]
    [ ELSE { <expression> | NULL } ]
    END 
  | <literal>
  | <sql_function> 

<search_condition> ::= 
  {
    <expression> { = | > | < | >= | <= | <> | != | LIKE | NOT LIKE | IN | NOT IN | IS NULL | IS NOT NULL | AND | OR | CONTAINS | BETWEEN } [ <expression> ]
  } [ { AND | OR } ... ] 

Examples

  1. Return all columns:
    SELECT * FROM [CData].[Default].Customers
  2. Rename a column:
    SELECT [CompanyName] AS MY_CompanyName FROM [CData].[Default].Customers
  3. Cast a column's data as a different data type:
    SELECT CAST(Balance AS VARCHAR) AS Str_Balance FROM [CData].[Default].Customers
  4. Search data:
    SELECT * FROM [CData].[Default].Customers WHERE Country = 'US';
  5. Return the number of items matching the query criteria:
    SELECT COUNT(*) AS MyCount FROM [CData].[Default].Customers 
  6. Return the number of unique items matching the query criteria:
    SELECT COUNT(DISTINCT CompanyName) FROM [CData].[Default].Customers 
  7. Return the unique items matching the query criteria:
    SELECT DISTINCT CompanyName FROM [CData].[Default].Customers 
  8. Summarize data:
    SELECT CompanyName, MAX(Balance) FROM [CData].[Default].Customers GROUP BY CompanyName
    See Aggregate Functions for details.
  9. Retrieve data from multiple tables.
    SELECT Customers.ContactName, Orders.OrderDate FROM Customers, Orders WHERE Customers.CustomerId=Orders.CustomerId
    See JOIN Queries for details.
  10. Sort a result set in ascending order:
    SELECT City, CompanyName FROM [CData].[Default].Customers  ORDER BY CompanyName ASC
  11. Restrict a result set to the specified number of rows:
    SELECT City, CompanyName FROM [CData].[Default].Customers LIMIT 10 
  12. Parameterize a query to pass in inputs at execution time. This enables you to create prepared statements and mitigate SQL injection attacks.
    SELECT * FROM [CData].[Default].Customers WHERE Country = @param
See Explicitly Caching Data for information on using the SELECT statement in offline mode.

Pseudo Columns

Some input-only fields are available in SELECT statements. These fields, called pseudo columns, do not appear as regular columns in the results, yet may be specified as part of the WHERE clause. You can use pseudo columns to access additional features from Apache Impala.

    SELECT * FROM [CData].[Default].Customers WHERE MyPseudocolumn = 'MyValue'
    

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Build 21.0.7930