Merge pull request #112973 from tfitzmac/0427functions3

added coalesce

Author: PRMerger15

articles/azure-resource-manager/templates/template-functions-comparison.md

@@ -8,12 +8,88 @@ ms.date: 04/27/2020
 
 Resource Manager provides several functions for making comparisons in your Azure Resource Manager (ARM) templates.
 
+* [coalesce](#coalesce)
 * [equals](#equals)
 * [greater](#greater)
 * [greaterOrEquals](#greaterorequals)
 * [less](#less)
 * [lessOrEquals](#lessorequals)
 
+## coalesce
+
+`coalesce(arg1, arg2, arg3, ...)`
+
+Returns first non-null value from the parameters. Empty strings, empty arrays, and empty objects are not null.
+
+### Parameters
+
+| Parameter | Required | Type | Description |
+|:--- |:--- |:--- |:--- |
+| arg1 |Yes |int, string, array, or object |The first value to test for null. |
+| additional args |No |int, string, array, or object |Additional values to test for null. |
+
+### Return value
+
+The value of the first non-null parameters, which can be a string, int, array, or object. Null if all parameters are null.
+
+### Example
+
+The following [example template](https://github.com/Azure/azure-docs-json-samples/blob/master/azure-resource-manager/functions/coalesce.json) shows the output from different uses of coalesce.
+
+```json
+{
+    "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
+    "contentVersion": "1.0.0.0",
+    "parameters": {
+        "objectToTest": {
+            "type": "object",
+            "defaultValue": {
+                "null1": null,
+                "null2": null,
+                "string": "default",
+                "int": 1,
+                "object": {"first": "default"},
+                "array": [1]
+            }
+        }
+    },
+    "resources": [
+    ],
+    "outputs": {
+        "stringOutput": {
+            "type": "string",
+            "value": "[coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2, parameters('objectToTest').string)]"
+        },
+        "intOutput": {
+            "type": "int",
+            "value": "[coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2, parameters('objectToTest').int)]"
+        },
+        "objectOutput": {
+            "type": "object",
+            "value": "[coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2, parameters('objectToTest').object)]"
+        },
+        "arrayOutput": {
+            "type": "array",
+            "value": "[coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2, parameters('objectToTest').array)]"
+        },
+        "emptyOutput": {
+            "type": "bool",
+            "value": "[empty(coalesce(parameters('objectToTest').null1, parameters('objectToTest').null2))]"
+        }
+    }
+}
+```
+
+The output from the preceding example with the default values is:
+
+| Name | Type | Value |
+| ---- | ---- | ----- |
+| stringOutput | String | default |
+| intOutput | Int | 1 |
+| objectOutput | Object | {"first": "default"} |
+| arrayOutput | Array | [1] |
+| emptyOutput | Bool | True |
+
 ## equals
 
 `equals(arg1, arg2)`