SELECT * FROM table_train_237 WHERE serum_25_oh_d_levels < 20
serum 25 ( oh ) d levels < 20 ng / ml.
CREATE TABLE table_train_237 (
    "id" int,
    "fasting_c_peptide" float,
    "fasting_plasma_glucose" int,
    "smoking" bool,
    "body_mass_index_bmi" float,
    "serum_25_oh_d_levels" int,
    "NOUSE" float
)