This set of SQL Multiple Choice Questions & Answers (MCQs) focuses on “SQL Create Table”.
1. Which of the following command is used to create a table in SQL?
a) CREATE
b) MAKE
c) DEVELOP
d) INSERT
View Answer
Explanation: The CREATE command is used to create a table in SQL. The same command can be used to create a database containing the table. The INSERT command is used to insert data inside the tables.
2. In SQL, the CREATE command can be put under which of the following category?
a) DDL (Data Definition Language)
b) DML (Data Manipulation Language)
c) DCL (Data Control Language)
d) TCL (Transaction Control Language)
View Answer
Explanation: In SQL, the CREATE command comes under the category of DDL (Data Definition Language) which is used to define the structure of the table. DML (Data Manipulation Language) is used to manipulate the data inside the table. DCL (Data Control Language) is used by the database administrator to configure security access to relational databases. TCL (Transaction Control Language) is used to commit or rollback the changes made by DML commands.
3. Consider the following syntax and tell whether it is the correct way to create a table in SQL or not.
CREATE TABLE TABLE_NAME column1 datatype CONSTRAINT column2 datatype CONSTRAINT column3 datatype CONSTRAINT . . . columnn datatype CONSTRAINT
a) True
b) False
View Answer
Explanation: The syntax for creating a table in SQL always contains an opening bracket before the first column name and a closing bracket and a semicolon at the end of the statement. For example –
CREATE TABLE TABLE_NAME (column1 datatype CONSTRAINT column2 datatype CONSTRAINT column3 datatype CONSTRAINT . . . columnn datatype CONSTRAINT);
4. It is necessary to specify a constraint for each column.
a) True
b) False
View Answer
Explanation: It is not necessary to specify a constraint for each column. Constraints are used to add some conditions to a column that restricts the column to remain true while inserting or updating or deleting data in that column.
5. Which of the following constraint are not present in SQL?
a) UNIQUE
b) NOT NULL
c) PRIMARY KEY
d) CANDIDATE KEY
View Answer
Explanation: CANDIDATE KEY is not present as a constraint in SQL. A Candidate key is the set of columns that can become the Primary Key. The column having the UNIQUE constraint cannot have any duplicate value. The column having the NOT NULL constraint cannot have any null value. The PRIMARY KEY constraint is a combination of UNIQUE and NOT NULL.
6. Which of the following is not a valid datatype in SQL?
a) INT
b) NUMBER
c) VARCHAR
d) DATE
View Answer
Explanation: NUMBER is not a valid datatype in SQL. INT, VARCHAR and DATE are used in SQL to receive an integer, string and date from the user respectively.
7. In SQL, a column having the UNIQUE constraint can have two null values.
a) True
b) False
View Answer
Explanation: The UNIQUE constraint is used in a column to restrain it from having similar values. Since, in SQL null means void, it can point towards anything and hence no two null values can be similar.
8. According to the following SQL statement, which of the column is specified as the primary key?
CREATE TABLE STUDENTS (ID INT PRIMARY KEY, NAME VARCHAR (15) NOT NULL, AGE INTNOT NULL, ADDRESS CHAR (25));
a) ID
b) NAME
c) AGE
d) ADDRESS
View Answer
Explanation: ID is the column that is specified as the primary key in the given statement. PRIMARY KEY is used to uniquely identify each record in the table.
9. How many columns will be created when the following SQL statement will get executed?
CREATE TABLE Employee (Eid INT, FName VARCHAR (50), LName VARCHAR (50), Email VARCHAR (50), Address VARCHAR (50), City VARCHAR (50));
a) 4
b) 5
c) 6
d) 3
View Answer
Explanation: The given SQL statement will produce a table having 6 columns – Eid, FName, LName, Email, Address and City.
10. Which of the following SQL statement is used to create a table by copying only the selected columns from another table?
a)
CREATE TABLE new_tablename AS ( SELECT * FROM old_tablename WHERE condition);
b)
CREATE TABLE new_tablename AS ( SELECT Column1, Column2...Columnn FROM old_tablename);
c)
CREATE TABLE new_tablename AS ( SELECT Column1, Column2...ColumnN FROM old_tablename1, old_tablename2...old_tablenamen);
d)
CREATE TABLE TABLE_NAME (column1 datatype CONSTRAINT column2 datatype CONSTRAINT column3 datatype CONSTRAINT ... columnn datatype CONSTRAINT);
Explanation:
CREATE TABLE new_tablename AS ( SELECT Column1, Column2...Columnn FROM old_tablename);
is used to create a table by copying only the selected columns from another table.
CREATE TABLE new_tablename AS ( SELECT * FROM old_tablename WHERE condition);
is used to create a table by copying all the columns from another table.
CREATE TABLE new_tablename AS ( SELECT Column1, Column2...ColumnN FROM old_tablename1, old_tablename2...old_tablenamen);
is used to create a table by copying selected columns from multiple tables.
CREATE TABLE TABLE_NAME (Column1 datatype CONSTRAINT Column2 datatype CONSTRAINT Column3 datatype CONSTRAINT ... Columnn datatype CONSTRAINT);
is the normal way to create a table.
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