How to send a message to Slack workspace members using an SQL statement?

INSERT INTO sqlmessenger_intf

            (oper_type,

             slack_app_name,

             send_to,

             body)

VALUES      ( 'S',--Operation type. "S" indicates to send a message to Slack workspace members via Slack API.

             'MySlackApp',--Specify which Slack app to use for sending this message.

             'U015NGUUGQ0',--The Slack workspace members who will receive this message. Separate multiple members with a comma (",").

             'This is a test message' --The content of the message.

);