Consider pipelines to stored procedures.
You could have the SP receive the input as JSON and generate dynamic SQL to do the INSERT, then EXECUTE IMMEDIATE the result. Also, you can use an INSERT that names the fields for which you provide values; then the other values will default to NULL. Like
singlestore> create table t(a int, b int, c int);
Query OK, 0 rows affected (0.03 sec)
singlestore> insert into t(a,c) values(1,3);
Query OK, 1 row affected (0.23 sec)
singlestore> select * from t;
+------+------+------+
| a | b | c |
+------+------+------+
| 1 | NULL | 3 |
+------+------+------+
1 row in set (0.03 sec)