FireDAC Components for HPCC

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 component:

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> 
    ]
  ] 
}

<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 hpcc::test::person
  2. Rename a column:
    SELECT [Name] AS MY_Name FROM hpcc::test::person
  3. Cast a column's data as a different data type:
    SELECT CAST(AnnualRevenue AS VARCHAR) AS Str_AnnualRevenue FROM hpcc::test::person
  4. Search data:
    SELECT * FROM hpcc::test::person WHERE Industry = 'Floppy Disks';
  5. The HPCC APIs support the following operators in the WHERE clause: =, <>, >, <, >=, <=, !=, IN, NOT IN.
    SELECT * FROM hpcc::test::person WHERE Industry = 'Floppy Disks';
  6. Return the number of items matching the query criteria:
    SELECT COUNT(*) AS MyCount FROM hpcc::test::person 
  7. Return the unique items matching the query criteria:
    SELECT DISTINCT Name FROM hpcc::test::person 
  8. Summarize data:
    SELECT Name, MAX(AnnualRevenue) FROM hpcc::test::person  GROUP BY Name
    See Aggregate Functions for details.
  9. Retrieve data from multiple tables.
    SELECT hpcc::test::person.firstname, hpcc::test::people.personid FROM hpcc::test::person OUTER JOIN hpcc::test::people ON hpcc::test::person.personid = hpcc::test::people.personid
    See JOIN Queries for details.
  10. Sort a result set in ascending order:
    SELECT Id, Name FROM hpcc::test::person  ORDER BY Name ASC
  11. Restrict a result set to the specified number of rows:
    SELECT Id, Name FROM hpcc::test::person 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 hpcc::test::person WHERE Industry = @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 HPCC.

    SELECT * FROM hpcc::test::person WHERE Pseudo = '@Pseudo'
    

Copyright (c) 2021 CData Software, Inc. - All rights reserved.
Build 21.0.7930