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Consider the following SQL command: CREATE TABLE MEMBER (MEM_ID INTEGER NOT NULL, NAME CHAR(15) NOT NULL, DATE_JOIN DATE, SEX CHAR(1) CHECK (SEX= ‘M’ OR SEX = ‘F’), ADDRESS VARCHAR(100) NOT NULL, PH_NO CHAR(15), PRIMARY KEY (MEM_NO), INDEX MEM_IDX (DATE_JOIN) );
Now answer the following questions:
NOT NULL ensures that
(A) Column cannot have blank value
(B) Column will not accept any value
(C) Column has a fixed value
(D) Column has a unique value
Answer:
By default, all columns in a table can hold null value ie., there is no particular value assigned for that column. The NOT NULL constraint ensures that a given column of a table is never assigned the null value.
So, the correct answer is (A)
Question 1 (ii)
By default format of date entered is
(A) DD-MM-YY
(B) MM-DD-YY
(C) YYYY-MM-DD
(D) DD-MM-YYYY
Answer:
The default format of date in SQL is YYYY-MM-DD.
Checking the options
- (A) DD-MM-YY - It is not the default format of date in SQL.
- (B) MM-DD-YY - It is not the default format of date in SQL.
- (C) YYYY-MM-DD - It is the default format of date in SQL.
- (D) DD-MM-YYYY - It is not the default format of date in SQL.
So, the correct answer is (C)
Question 1 (iii)
The ______ constraint ensures that the value entered specifies a certain condition.
(A) NOT NULL
(B) NULL
(C) CHECK
(D) All of these
Answer:
Checking the options
- (A) NOT NULL - Enforces a column to not accept null values.
- (B) NULL - The NULL keyword is used to specify that a column can accept null values.
- (C) CHECK - Limits the values that can be entered in certain columns based on a condition.
- (D) All of these
From the above explanation, it is clear that the CHECK constraint ensures that the value entered specifies a certain condition.
So, the correct answer is (C)
Question 1 (iv)
PRIMAY KEY in above example ensures that
(A) MEM_ID is entered primarily
(B) MEM_ID will hold a uniquely identified value
(C) MEM_ID will not remain blank
(D) All of these
Answer:
The primary key of a table uniquely identifies each record in the table. The value of the primary key should be unique and not null .
Checking the options
- (A) MEM_ID is entered primarily - True for a primary key.
- (B) MEM_ID will hold a uniquely identified value - True for a primary key.
- (C) MEM_ID will not remain blank - True for a primary key.
- (D) All of these
Primary key ensures all the conditions given in the options.
So, the correct option is (D)
Question 1 (v)
The INDEX command in above example will
(A) Create an index on field DATE_JOIN
(B) Create an index namely MEM_IDX
(C) Both (a) and (b)
(D) None of the above
Answer:
The index command in MySQL creates indexes. They are used to retrieve data from the database more quickly than otherwise. The syntax to create an index is as follows:
CREATE INDEX index_name
ON table_name ( column1 , column2 , ...);
The command INDEX MEM_IDX (DATE_JOIN) creates an index named MEM_IDX on the field DATE_JOIN.
Checking the options
- (A) Create an index on field DATE_JOIN
- (B) Create an index namely MEM_IDX
- (C) Both (a) and (b)
- (D) None of the above
Both option (A) and (B) are correct.
So, the answer is (C)
