PostgreSQL Null value in column violates not-null constraint

Null value in column violates not-null constraint in PL/pgSQL

Not-null constraint

The cause of error: Null value in column violates not-null constraint in PL/pgSQL.

Create Students table

CREATE TABLE test.students
(
    id numeric NOT NULL,
    first_name character varying(50) NOT NULL,
    last_name character varying(50) NOT NULL,
    entry_date timestamp without time zone DEFAULT now(),
    address_id numeric,
    CONSTRAINT studentss_pkey PRIMARY KEY (id)
);

CREATE TABLE
Query returned successfully in 506 msec.

Wrong insert

INSERT INTO test.students 
(id, first_name, last_name) 
VALUES (3, null, 'Evans');

ERROR: null value in column “first_name” violates not-null constraint
DETAIL: Failing row contains (3, null, Evans, 2017-02-18 08:33:08.125874, null).

Query returned successfully in 423 msec.

Correct insert

INSERT INTO test.students 
(id, first_name, last_name) 
VALUES (3, 'Sarah', 'Evans');

INSERT 0 1

Query returned successfully in 409 msec.