Do not try to determine the size of the StuID. also add restriction key operation and just to use DROP before CREATE for example:
DROP TABLE Student; CREATE TABLE Student ( StuID NUMBER, StuName VARCHAR2(50), Phone VARCHAR2(20), constraint pk_Student PRIMARY KEY (StuID)); DROP TABLE Program; CREATE TABLE Program ( ProCode VARCHAR2(12), ProTitle VARCHAR2(50), constraint pk_Program PRIMARY KEY (ProCode));
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