Question

-What happens if you attempt to insert an existing value into the primary key. After insertion you must change the value to a non-existing value The DBMS will allow you to insert, with a warning message The DBMS will allow you to insert, and modify the value automatically The DBMS will not allow you to insert

Answer 1

Answer

The DBMS will not allow you to insert

Explanation

Primary Key

A primary key used for the purpose of uniquely identifiying each record in a database table.

Primary keys must contain "UNIQUE" values

Primary keys cannot contain NULL value

Example

/* Create a table called NAMES */
CREATE TABLE NAMES(Id integer PRIMARY KEY, Name text);

/* Create few records in this table */
INSERT INTO NAMES VALUES(1,'Tom');
INSERT INTO NAMES VALUES(1,'Lucy');

/* Display all the records from the table */
SELECT * FROM NAMES;

if you observe that in the query we are trying to insert '1' again lets run the query and see the result

/* Create a table called NAMES */ CREATE TABLE NAMES(ID integer PRIMARY KEY, Name text); $sqlite3 database. sdb < main.sql 1 Tom Error: near line 8: UNIQUE constraint failed: NAMES. I 5 /* Create few records in this table Sovo u WNE INSERT INTO NAMES VALUES(1, 'Tom'); INSERT INTO NAMES VALUES(1, 'Lucy'); 10 /* Display all the records from the table */ 11 SELECT * FROM NAMES;

As you can see there is an error

"UNIQUE" constraint failed

WN /* Create a table called NAMES */ CREATE TABLE NAMESCID integer PRIMARY KEY, Name text); $sqlite3 database. sdb < main.sql 1 Tom 2 Lucy 5 /* Create few records in this table INSERT INTO NAMES VALUES(1, 'Tom'); INSERT INTO NAMES VALUES(2, 'Lucy'); B Bovo u 10 /* Display all the records from the table */ 11 SELECT * FROM NAMES;

Now we changed the value '1' to '2'

now query runs perfectly

Hence, The DBMS will not allow you to insert

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