node-red, MySQL error - mysql

Question

Get an error when writing to the database
The function for it:
var newMsg = { payload: msg.payload };
newMsg.topic="insert into MyTable (a,b,c,d,e,f,g) values (newMsg.payload)"
The incoming payload debug shows
payload: "B0:AC:A2:AC:07:F4","Ready","893901","860990","online","876","333"
The error I get from the database node (nore-red-node-mysql) is
"Error: ER_WRONG_VALUE_COUNT_ON_ROW: Column count doesn't match value
count at row 1"
The strange thing to me is that if I try a
newMsg.topic="insert into MyTable (a,b,c,d,e,f,g) values (\"B0:AC:A2:AC:07:F4\",\"Ready\",\"893901\",\"860990\",\"online\",\"876\",\"333\")"
it works perfectly...
Where is the trick?

Answer 1

There is no trick.
This is because the node-red-node-mysql and node-red-contrib-sqldbs nodes do not do any query substitution.
This means that what gets sent to the database is exactly what is in the msg.topic field. In this case that would have been:
insert into MyTable (a,b,c,d,e,f,g) values (newMsg.payload)
Which mysql will read as trying to pass a single value to a query expecting 7 values.
You will have to build the full query (and do your own variable escaping if needed) in a function node before passing the message to the database node.

Answer 2

at the end I solved it this way:
var data = msg.payload.split(",");
msg.payload = {};
msg.payload.a=data[0];
msg.payload.b=data[1];
msg.payload.c=data[2];
msg.payload.d=data[3];
msg.payload.e=data[4];
msg.payload.f=data[5];
msg.payload.g=data[6];
insert into MyTable (a,b,c,d,e,f,g) values ('" + data[0] + "','" + data[1] + "','" + data[2] + "','" + data[3] + "','" + data[4] + "','" + data[5] + "','" + data[6] + "')";
return msg;