Merge pull request #280 from tigergraph/DOC-2408-aggreg-func-value-when-empty

DOC-2408-aggreg-func-value-when-empty

Author: victorleeTG

modules/querying/pages/func/aggregation-functions.adoc

@@ -4,7 +4,14 @@ This page lists the aggregation functions available in the GSQL query language.
 
 [NOTE]
 ====
-The ``DISTINCT`` keyword can be used to include repeated values only once when aggregating.
+If the ``DISTINCT`` option is used, then duplicate values are excluded.
+By default, duplicate values are included.
+
+Example:
+
+``sum([2,2,2]) ``returns 6.
+
+`sum(DISTINCT [2,2,2])` returns 2.
 ====
 
 == avg()
@@ -18,6 +25,7 @@ The ``DISTINCT`` keyword can be used to include repeated values only once when a
 === Description
 
 Returns the average of all elements in a set or bag. The function can only take set/bag expressions whose members are numeric types.
+Returns 0 if the input set is empty.
 
 [discrete]
 === Return type
@@ -55,6 +63,7 @@ avg([3, 2, 1]) -> 2
 === Description
 
 Returns the size of the set or bag.
+Returns 0 if the input set is empty.
 
 [discrete]
 === Return type
@@ -92,6 +101,7 @@ count([1, 1, 2, 2) => 4
 
 Returns the member with the maximum value in a set or bag.
 The function can only take set/bag expressions whose members are numeric types.
+Returns 0 if the input set is empty.
 
 [discrete]
 === Return type
@@ -128,6 +138,7 @@ max([1, 1, 3, 3]) => 3
 === Description
 
 Returns the member with the minimum value in a set or bag. The function can only take set/bag expressions whose members are numeric types.
+Returns 0 if the input set is empty.
 
 [discrete]
 === Return type
@@ -164,6 +175,7 @@ min([1, 1, 3, 3]) => 1
 === Description
 
 Returns the standard deviation of all members in a set or bag, assuming the input is a sample.
+Returns 0 if the input set is empty.
 
 This function uses `N - 1` as the denominator, and should be used when taking a sample of the population for an unbiased estimate. When the standard variation of the entire population is being calculated, `stdevp` should be used.
 
@@ -205,6 +217,7 @@ stdev([1, 2, 3, 4, 5]) => 1.5811388300842
 === Description
 
 Returns the standard deviation of all members in a set or bag, assuming the input is the population.
+Returns 0 if the input set is empty.
 
 This function uses `N` as the denominator, and should be used when calculating the standard deviation for an entire population. When the standard variation of only a sample of the population is being calculated, `stDev` should be used.
 
@@ -246,6 +259,7 @@ stdevp([1, 2, 3, 4, 5]) => 1.4142135623731
 === Description
 
 Returns the sum of all members in a set or bag. The function can only take set/bag expressions whose members are numeric types.
+Returns 0 if the input set is empty.
 
 [discrete]
 === Return type