Figure: Table with `NOT NULL` Integrity Constraints

Table `EMPLOYEES`

Columns: ID, LNAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO

row 1: 100, King, AD_PRES, , 17-JUN-87, 24000, , 90

row 2: 101, Kochhar, AD_VP, 100, 21-SEP-89, 17000, , 90

row 3: 102, De Hann, AD_VP, 100, 13-JAN-93, 17000, , 90

row 4: 103, Hunold, IT_PROG, 102, 03-JAN-90, 9000, , 60

The `JOB` column is annotated with the text "`NOT NULL` Constraint (no row may contain a null value for this column)".

The `COMM` column is annotated with the text "Absence of `NOT NULL` Constraint (any row can contain a null for this column)".

The constraint on `LNAME` is specified by:

    ALTER TABLE "emp" MODIFY "ENAME" NOT NULL.