wrap drop statements inside blocks to avoid exception when running first time

plsql/item.sql

@@ -1,5 +1,14 @@
 PROMPT Creating Table 'ITEM'
-DROP TABLE item;
+
+BEGIN
+  EXECUTE IMMEDIATE 'DROP TABLE item';
+EXCEPTION
+  WHEN OTHERS THEN
+    IF SQLCODE != -942 THEN
+      RAISE;
+    END IF;
+END;
+
 CREATE TABLE item
   (
     name    VARCHAR2(100) NOT NULL,
@@ -7,3 +16,5 @@ CREATE TABLE item
     quality NUMBER(6) NOT NULL
   );
 /
+
+SHOW ERRORS;

plsql/item_with_id.sql

@@ -1,5 +1,14 @@
 PROMPT Creating Table 'ITEM' with auto-increment primary key 'ID'
-DROP TABLE item;
+
+BEGIN
+  EXECUTE IMMEDIATE 'DROP TABLE item';
+EXCEPTION
+  WHEN OTHERS THEN
+    IF SQLCODE != -942 THEN
+      RAISE;
+    END IF;
+END;
+
 CREATE TABLE item
   (
     id      NUMBER(6) NOT NULL,
@@ -13,19 +22,29 @@ ALTER TABLE item ADD (
   CONSTRAINT item_pk PRIMARY KEY (ID));
 /
 
-DROP SEQUENCE item_id_seq;
+BEGIN
-CREATE SEQUENCE item_id_seq 
+  EXECUTE IMMEDIATE 'DROP SEQUENCE item_id_seq';
-  INCREMENT BY 1 
+EXCEPTION
-  START WITH 1 
+  WHEN OTHERS THEN
+    IF SQLCODE != -2289 THEN
+      RAISE;
+    END IF;
+END;
+
+CREATE SEQUENCE item_id_seq
+  INCREMENT BY 1
+  START WITH 1
   MAXVALUE 999999
-  MINVALUE 1 
+  MINVALUE 1
   NOCYCLE;
 /
 
-CREATE OR REPLACE TRIGGER item_bis_trg 
+CREATE OR REPLACE TRIGGER item_bis_trg
-  BEFORE INSERT ON item 
+  BEFORE INSERT ON item
-  FOR EACH ROW 
+  FOR EACH ROW
 BEGIN
     SELECT item_id_seq.NEXTVAL INTO :new.id FROM dual;
 END;
 /
+
+SHOW ERRORS;