SQL Query error : sqlKind = UNINITIALIZED

Hello Appian Community 

Goal : I'm looking for a way to call a specific sequence in my database without having a huge amount of process nodes for each sequence I have.
Additional information : Depend on the context, I have to call a sequence. So for 50 contexts, I have 50 sequences. I previously made 50 nodes to call my specific sequence depend on the context.
What I've newly done : In my process model, I have a node to create an SQL query where I inject this query to call the sequence I want, depend on a given context.

As you can see, the query variable "ac!sequence" is my SQL where I try to get the NEXTVAL of a given known DB sequence.
But by doing that, my process model rise an error : 
"There was a problem executing the SQL query. SQL Message : Invalid SQL type: sqlKind = UNINITIALIZED"

Questions :
I guess is not a proper way to do that, but what can I do to fix it (if it's possible) ?
How to reach my goal to call a specific sequence in one (or a bit more) node ?

have a nice days all 
Gabriel