This is an overview of all functions available within the DQL. Functions can be used to aggregate (sum, average ..) or do custom tranformations (ceiling, flooring, …)

  • avg

    The avg function is an aggregation function and calculates the average of all values passed as a parameter and returns the result.

  • chisquare

    The chisquare function calculates the chisquare significance based on the submitted values. If the chisquare test is not appropriate, it will return null.

  • coalesce

    The coalesce function is used to transform a null value into something useful. If the parameter passed to coalesce is null, the second parameter will be returned and otherwise the first parameter.

  • count

    The count function is an aggregation function and returns the amount of rows fetched from the dataset.

  • cumulate

    The cumulate function does the same as the sum function, but is no aggregation function. This allows cumulative representations of data.

  • distinctcount

    The distinctcount function is very similar to the count function, but only counts distinct values - duplicates are ignored.

  • if

    The if function is used to apply a condition on a column. The first parameter is a condition, the second parameter is returned if the condition returns true and the third parameter is returned if the condition is false.

  • max

    The max function is an aggregation function which is capable of returning the maximum value from a column in a group.

  • min

    The min function is an aggregation function which allows to extract the lowest value from a group. The opposite function of this is the max function.

  • participates

    The participates function returns a flag, saying whether an experiment participates in an entity or not. For instance, this is useful to determine whether a session participates in an experiment.

  • pres

    The pres function can be used to read the result of the psum function for a single channel which comes from the experiment.

  • psum

    The psum function is an aggregation function and can be used on participation fields. It will sum the participations together and return a total sum mask for all channels.

  • round

    The round function rounds the values down to zero decimal places, or to the amount of decimal places submitted in the second parameter.

  • stddev

    The standard deviation function is an aggregation function which calculates the standard deviation of the submitted values.

  • sum

    The sum function is an aggregation function, it rolls all rows together and returns the total sum of the values submitted in the parameter.

  • time

    The time function returns the current time, in the same way as they are stored in all time columns. It returns the amount of seconds passed since 1970.

  • timefloor

    The timefloor function rounds the time value to the closest interval value. This allows grouping based on time.

  • variation

    The variation function is an aggregation function and calculates the variation of the submitted values.