# Multiply (Merge) Like the multiple operator in jq, depending on the operands, this multiply operator will do different things. Currently numbers, arrays and objects are supported. ## Objects and arrays - merging Objects are merged deeply matching on matching keys. By default, array values override and are not deeply merged. Note that when merging objects, this operator returns the merged object (not the parent). This will be clearer in the examples below. ### Merge Flags You can control how objects are merged by using one or more of the following flags. Multiple flags can be used together, e.g. `.a *+? .b`. See examples below - `+` to append arrays - `?` to only merge existing fields - `d` to deeply merge arrays ### Merging files Note the use of `eval-all` to ensure all documents are loaded into memory. ```bash yq eval-all 'select(fileIndex == 0) * select(fileIndex == 1)' file1.yaml file2.yaml ```