sql-server-samples/samples/manage/sql-assessment-api/docs/Reference/DataTransformation/aggregate.md

Data transformation: aggregate

Takes all data rows returned from probes or previous transformations and calculates aggregate values for specified columns. If grouping was specified, returns an aggregate row for every group. Returns one row otherwise.

Paramters

Parameter	Required	Type	Description
map	Required	Map	Maps column names to aggregate functions
group	Optional	String or Array of strings	Names of columns used for grouping

Grouping

By default aggregate functions are applied to all data records returned by probes or previous transformations. Optionally, aggregates may be applied to groups of rows having the same value(s) in selected column(s). it works much like GROUP BY T-SQL clause.

Example 1

In this example blocked_spid becomes the number of unique non-null blocked_spids, block_time_min becomes the minimum of all block_time_mins. Other columns are removed.

"transform": {
    "type": "aggregate",
    "map": {
        "blocked_spid": "count",
        "block_time_min": "min"
    }
}

Example 2

In this example the transformation count non-unique non-null RecoveryUnitIds.

"transform": {
    "type": "aggregate",
    "map": {
        "RecoveryUnitId": {
            "type": "count",
            "distinct": false
        },
        "blocked_spid": "count",
        "block_time_min": "min"
    }
}

Example 3

In the following example the transform constructs a string containing a comma-separated list of all publications for each publisher_db.

"transform": {
    "type": "aggregate",
    "group": "publisher_db",
    "map": {
        "publication": "join"
    }
}

Aggregate Functions

and/or

Calculates 'and'/'or' aggregate value for boolean values. Null, DBNull, empty string, empty array, and string 'false' are converted to false. Non-empty string, non-empty array, and string 'true' are converted to true.

array

Collects all values into an array.

count

Count all values.

Parameter	Required	Type	Default	Description
distinct	Optional	Bool	true	If true count only distinct values
notNull	Optional	Bool	true	if true count only non-null values

join

Converts values to string and joins them into string separated by comma by default.

Parameter	Required	Type	Default	Description
trim	Optional	Bool	true	If true, trim white space from the beginning and the end of each value
separator	Optional	String	', '	A string used to separate values
limit	Optional	Int	0	When limit > 0, join returns a string containing not more than first limit items with ellipsis replacing the rest. E.g. when limit=3, for [1,2,3,4,5] join returns "1, 2, 3, ..."
distinct	Optional	Bool	true	Skips repeating values. E.g. for [cat,lion,cat,cat,tiger,lion] join returns "cat, lion, tiger"
comparison	Optional	Comparison	CurrentCulture	Specifies the culture, case, and sort rules to be used for selecting distinct values. See StringComparison Enum for allowed values and more details.

max/min

Calculates max/min value. For numeric values only.

sum

Calculates sum of all the values. For numeric values only.