Table Creation/// NOT NULL (check constraint)

Everything (Table Creation including Primary ,Foreign key ,Check constraint and giving user defined CONSTRAINT NAME for NOT NULL CONSTRAINT) in a single Script ;without using alter command for predefined constraints till design time


CREATE TABLE   STUDENTS_MAST(
N_STUDID NUMBER(5),CONSTRAINT PK_STUDID  PRIMARY KEY(N_STUDID))


CREATE TABLE STUDENT_TEAM (
N_STDTMID NUMBER(10) ,CONSTRAINT PK_STUDENT_TEAM PRIMARY KEY(N_STUDTMID),
N_STUDID NUMBER(10),CONSTRAINT FK_STUD_TEAM_EMPID FOREIGN KEY(N_STUDID) REFERENCES STUDENTS_MAST(N_STUDID),
C_TLFLAG CHAR(1) ,CONSTRAINT CK_STUD_TEAM_TLFLAG CHECK (C_TLFLAG IN ('Y','N')) ,
D_STDATE DATE CONSTRAINT NN_STUD_TEAM_STDATE NOT NULL,
D_ENDDATE DATE CONSTRAINT NN_STUD_TEAM_ENDATE NOT NULL,
D_ENTRYDAT DATE DEFAULT SYSDATE )


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CREATE TABLE STUDENT_TEAM (N_STDTMID NUMBER(10) CONSTRAINT NN_STUDENT_STATUS_TMID NOT NULL)


ALTER TABLE STUDENT_STATUS ADD ( CONSTRAINT NN_ST_STATUS_TMID CHECK (N_STDTMID IS NOT NULL))


Both Scripts will restrict not null values but error code will be different first script results


ORA-01407: cannot update to NULL

ORA-01400: cannot insert NULL into N_STDTMID

second script results


Another difference is the null(nullable) field will be true when null is checked by first script but it will not be for second second script
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During check constraint creation if already exists some records in the particular table which violates the new check constraint.This error will be displayed
ORA-02293: cannot validate (##########) - check constraint violated

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