Explain PL/SQL variable declarations and data types (NUMBER, VARCHAR2, DATE, BOOLEAN, etc.)

How it works

Declare variables in the DECLARE section with a datatype and optional default via := or DEFAULT. Common scalar types are NUMBER, VARCHAR2(n), DATE, and BOOLEAN (a PL/SQL-only type — no SQL column can be BOOLEAN). A variable declared NOT NULL must be given an initial value at declaration time.

DECLARE
  v_employee_id   NUMBER := 100;
  v_last_name     VARCHAR2(50) := 'King';
  v_hire_date     DATE := SYSDATE;
  v_is_active     BOOLEAN := TRUE;
BEGIN
  DBMS_OUTPUT.PUT_LINE(v_last_name || ' hired on ' || TO_CHAR(v_hire_date, 'DD-MON-YYYY'));
END;
/

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