LISTEN [TABLE] channel_name [DATABASE database_name]
The LISTEN command is used to start receiving notifications for a given channel/table. Nothing is done if the current connection is registered as a listener for this notification channel. The optional DATABASE parameter is ignored if the TABLE flag is not specified.
The optional TABLE flag specifies that you want to receive notification for a given table. The DATABASE parameter can be used to identify which database to use (or the current database will be used). LISTENING to a table means you'll receive notification about all the write operations in that table. In the case of TABLE, the channel_name can be *, which means you'll start receiving notifications from all the tables inside the specified database.
OK string or error value (see SCSP protocol).
> LISTEN channel1 OK