ERROR: only one relationship type is allowed for MERGE open cypher query agensgraph - cypher

Question

Is the below realtionship creation allowed in open cypher query I am trying this in agensgraph,
MATCH (mc: mat_comp)
MATCH (p:plant)
MATCH (mb: material)
WHERE mc.component = mb.material and mc.plant=p.b_plant
MERGE (mc) <- [ comp_2_p] - ( p)
;
ERROR: only one relationship type is allowed for MERGE
What mistake I am doing... because mat_comp and plant nodes has plant as common mat_comp and material nodes has material as common
mat_comp
has material column
plant column
p: plant
mb:
material colum
MATCH (mc: mat_comp)
MATCH (p:plant)
MATCH (mb: material)
WHERE mc.comp = mb.material and mc.plant=p.b_plant
RETURN mc.comp, mb.material, mc.plant, p.b_plant;
comp | material | plant | b_plant
------------+------------+-------+--------------
"10" | "10" | "33" | "33"
=# \d material
material | character varying(50) | | | |
b_plant | character varying(50) |
=# \d mat_comp
material | character varying(50) | | | |
comp | character varying(50) | | | |
plant | character varying(50) | | | |
-# \d plant
--------------+-----------------------+-----------+----------+---------+-------------
b_plant | character varying(50) |

Answer 1

I think your query has a simple mistake in MERGE clause.
To cut to the point. You can use this query
MERGE (mc) <- [:comp_2_p] - (p)
The mistake is colon.
The word after the colon is type of component (such as node and edge).
The word before the colon is like a pronoun in Cypher clause (I don't know its exact name.).
If you still have another ERROR using above query, you should check whether the elabel "comp_2_p" is declared or not.