Oracle 11g Release 2

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SELECT * FROM v$version;


BANNER


Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production

PL/SQL Release 11.2.0.2.0 - Production

CORE	11.2.0.2.0	Production

TNS for Linux: Version 11.2.0.2.0 - Production

NLSRTL Version 11.2.0.2.0 - Production


CREATE TABLE user_ -- Oracle doesn't let you create a table called "user"
(
  user_id INTEGER NOT NULL PRIMARY KEY,
  user_name VARCHAR (25) NOT NULL  
);
INSERT INTO user_ (user_id, user_name)
SELECT 1, 'user_1' FROM dual
UNION
SELECT 2, 'user_2' FROM dual;


2 rows affected

SELECT * FROM user_ ORDER BY user_id;


USER_ID
USER_NAME


1
user_1

2
user_2


CREATE TABLE message
(
  message_id INTEGER NOT NULL PRIMARY KEY,
  sender_id INTEGER,
  message_text VARCHAR (100) NOT NULL,
  FOREIGN KEY (sender_id) REFERENCES user_ (user_id)
);
INSERT INTO message 
SELECT 1, 1, 'm1' FROM dual
UNION 
SELECT 2, 1, 'm2' FROM dual
UNION 
SELECT 3, 2, 'm3' FROM dual
UNION 
SELECT 4, 2, 'm4' FROM dual;
4 rows affected

SELECT * FROM message;


MESSAGE_ID
SENDER_ID
MESSAGE_TEXT


1
1
m1

2
1
m2

3
2
m3

4
2
m4


INSERT INTO message VALUES (5, 56, 'mxxxx');
ORA-02291: integrity constraint (FIDDLE_SFUMLUOUAPJRGZRTEMCW.SYS_C00313901) violated - parent key not found