Retrieves the schema description of a Salesforce sobject and emits a SOQL query listing only the fields that are 'createable=true'.

getCreateableFieldsQuery.zsh

#!zsh

if [ ! -n "$2" ]
then
	help_text=$( cat <<ENDxxx
$0 allows you to specify a Salesforce object defined within 
an org and returns a SOQL query that returns only the createable
fields of that object. Use this query to quickly extract a CSV 
of the fields of that object that you can insert or upsert to 
an org without having to determine which fields will fail because
they cannot be inserted or upserted (for example, formula fields or 
automatically numbered name fields.)

Usage: $0 <Salesforce object> <Salesforce org alias>
  where
    <Salesforce object> is the API name of a Salesforce Custom Object. This is
      used to call "sfdx force:schema:describe" as the value for the 
      '--sobjecttype' parameter
    <Salesforce org alias> is the alias of the org in which the <Salesforce object> is
     defined. This is used to call "sfdx force:schema:describe" as the value
      for the '--target-org' parameter (formerly the '--targetusername'
      parameter.) It is assumed that this org has already been authorized
      with sfdx:
        sfdx auth:web:login --instanceurl="<url of target org>" 
        --setalias="<Salesforce org alias>"

$0 requires sfdx and jq commands to be in your PATH.

ENDxxx
)
	echo "$help_text"
	exit
else
    CUSTOMOBJ=$1
	ORG=$2
fi

sfdx force:schema:sobject:describe --sobjecttype $CUSTOMOBJ --target-org $ORG | jq --arg customObject $CUSTOMOBJ '[ .fields[] | if .createable then .name else empty end ] | join(", ") | "SELECT " + . + " FROM " + $customObject'