Test Series

Question

Examine the structure of the EMPLOYEES table:

EMPLOYEE_ID NUMBER Primary Key

FIRST_NAME VARCHAR2(25)

LAST_NAME VARCHAR2(25)

Assume all the following four options are executed in the same sequence order. Which statement will not insert a row into the table?

 

a. INSERT INTO employees(first_name,last_name, employee_id) VALUES ( 1000, ‘John’,‘Smith’);

b. INSERT INTO employees VALUES (‘1000’,‘John’,NULL);

c. INSERT INTO employees (employee_id) VALUES (1000);

d. INSERT INTO employees (employee_id, first_name, last_name) VALUES ( 1000, ‘John’,‘’);

Answer 1

There are various formats of inserting the values in a table. In this case we are given three parameters the EMPLOYEE_ID,FIRST_NAME and LAST_NAME. Out of this the EMPLOYEE_ID is the primary key so it can't be null. Rest of the two parameters can be null. If we do not specify the coloumn name when we are inserting the values then the order that is interpreted for the values is the way it was defined during the table creation. If we are mentioning which coloumns we are filling the data then the order should be as mentioned in the insert command.

lets check the options:

a: This option is wrong as the order in which it is said to insert the data doesnot match with the parameters.

b:Correct As the values are inserted according to the order specified during the creation of table

c:Correct Only the coloumn name which is specified that value is being entered .

d:Correct The last value is null in this case.

So option a will not insert a row.

Comments

nice explanation

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yes, but the answer is given as "d", so i was confused

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The only problem that could have been with the option d is the value of the last_name as it is nothing but as the not null constraint is also not given so I guess it should be correct. The a option is not right as the data types dont match only.

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see what you are saying is correct obviously but what i think its a printing mistake rather a typing mistake considering it a typing mistake and considering it to be

INSERT INTO employees( employee_id, first_name,last_name) VALUES ( 1000, ‘John’,‘Smith’);

lets assume it to be correct 

 

But what i feel is option d inserting '' is not allowed ,yeah you can insert null but '' is not allowed . This is what i guess please confirm me if i am wrong or right.

But the problem is my test series has given option b . Is it because '1000' is considered a string instead of number?

 

There is too much confusion , plz @Arjun Sir clear it

Answer 2

employee_id have been created to accept NUMBER but you are passing STRING to it so, will not insert a row into the table.

Answer 3

 

see what @anjali007  saying is correct obviously but what i think its a printing mistake rather a typing mistake considering it a typing mistake and considering it to be

INSERT INTO employees( employee_id, first_name,last_name) VALUES ( 1000, ‘John’,‘Smith’);

lets assume it to be correct 

 

But what i feel is option d inserting '' is not allowed ,yeah you can insert null but '' is not allowed . This is what i guess please confirm me if i am wrong or right.

But the problem is my test series has given option b . Is it because '1000' is considered a string instead of number?

 

There is too much confusion , plz @Arjun Sir clear it