Aparavi Query Language - Variables

Variables

Variables are used to define values and expressions that can be utilized within the SELECT statement or by other variables. Declarations are set prior to the SELECT statement.

Variables are complete expressions, using functions, physical columns and aliases. A variable name must begin with @ . Variables beginning with @@ are system variables reserved to set options or settings for the query.

Since each SET statement is an independent command within the AQL statement, each statement should end with a semi-colon ( ; )

SET @USER = 'JOHN.SMITH';

EXAMPLE

SET @USER = 'JOHN.SMITH';
SET @@LEFT_JOIN=false;
 
SELECT
    osOwner as Owner,
    path as Location,
    classification as Classification
WHERE
    osPermission like CONCAT('%/',@USER,'%') AND
    classification like 'U.S.%';

Defines a variable @USER to JOHN.SMITH
Sets the System variable LEFT_JOIN to FALSE (will return only rows with an osPermission and Classification value - similar to an INNER JOIN)
Returns Owner, Path, and Classification for rows that have a Classification starting with U.S. and whose osPermission is */JOHN.SMITH*

SYSTEM VARIABLES

System Variable	Description
@@ADD_DEFAULT_COLUMNS	When TRUE, all columns specified by `@@DEFAULT_COLUMS` are added to the column `SELECT` list. If `@@DEFAULT_COLUMNS` is not specified, the system default columns will be used. `SET @@ADD_DEFAULT_COLUMNS=true;`
@@DEFAULT_COLUMNS	List of columns that will be added to the column `SELECT` list if `@ADD_DEFAULT_COLUMS` is set to TRUE. `SET @@DEFAULT_COLUMNE=Name,ParentPath;`
@@DISABLE_AGGREGATION	Disables aggregation expressions. If a query resolves to an aggregation, an error will be thrown. `SET @@DISABLE_AGGREGATION=true;`
@@LEFT_JOIN	Defaults is `TRUE` . This setting defines if the query should operate like a LEFT JOIN or an INNER JOIN. When LEFT JOIN is true, it will return all rows where the column is NULL/missing even when it is contained in the WHERE clause. When LEFT JOIN is FALSE, those rows will be skipped. `SET @@LEFT_JOIN=true;`
@@CONTEXTWORDS	Sets the number of words to retrieve for the context columns for search or classification hits. For example, setting this value to 25 will return 25 words for the `searchHitWordsBefore` column. `SET @@CONTEXTWORDS=25;`
@@CONTEXTCOUNT	Sets the maximum number of hits for search and classification hits to return. A document may have hundreds of hits but by using the value, the number of hits can be set. `SET @@CONTEXTCOUNT=25;`