SQL MCQ Questions and answers

SELECT name FROM staffinfo WHERE salary IN (10000, 25000);

This query correctly selects the names of staff members whose salary is either 10,000 or 25,000. The correct answer is Option B because it selects the names of staffs with salaries of 10,000 or 25,000, as required by the question.

To insert values into a table using SQL, you should use the INSERT INTO statement, followed by the table name and the keyword VALUES. The correct syntax is:
Option C: INSERT INTO student VALUES (
This option is the correct choice for inserting values into the "student" table.

Option A: INSERT student VALUES (
This option is incorrect because it lacks the "INTO" keyword.

Option B: INSERT VALUES (
This option is incorrect because it is missing the table name.

Option D: INSERT VALUES INTO student (
This option is also incorrect as it has an incorrect order of keywords.

So, the correct answer is Option C as it follows the proper syntax for inserting values into the "student" table in SQL.

The type of join that involves joining two or more tables based on a specified column value not equaling a specified column value in another table is known as a NON-EQUIJOIN. In a non-equijoin, the condition for joining is based on inequality or non-equality of values between the columns in different tables.

Option A: EQUIJOIN - This type of join matches tables based on the equality of column values and is not relevant to non-equijoin.
Option C: OUTER JOIN - An outer join includes unmatched rows from one or both tables but doesn't specifically indicate non-equality.
Option D: NATURAL JOIN - A natural join matches columns with the same name in the joined tables, but it is not related to non-equality.

So, the correct answer is Option B: NON-EQUIJOIN, as it accurately describes a join based on non-equality of column values in different tables.

In SQL, the command used to change a table's storage characteristics is ALTER TABLE. The ALTER TABLE statement allows you to modify an existing table, which can include changes to the table's structure, storage, or other attributes.

Option B: MODIFY TABLE is not a standard SQL command.
Option C: CHANGE TABLE is also not a standard SQL command.
Option D: "None of these" is incorrect because ALTER TABLE is the correct command for this purpose.

So, the correct answer is Option A: ALTER TABLE.

In SQL, the Data Definition Language (DDL) is used to define, manage, and modify the structure of a database. DDL commands are primarily responsible for creating, altering, or deleting tables, schemas, and other database objects. Among the options provided:

Option C: UPDATE is not a data definition language command. UPDATE is a Data Manipulation Language (DML) command used to modify data within existing tables, not to define or manage the structure of the database.

The other options, REVOKE, RENAME, and GRANT, are DDL commands used for managing user privileges, renaming database objects, and controlling access, respectively.
So, the correct answer is Option C: UPDATE.

In SQL, the 'AS' clause is used for renaming columns or tables. It is primarily used for the rename operation. When you use the 'AS' clause, you can give an alias or alternate name to a column or a table, making it more readable or meaningful in the query's result. So, the correct answer is Option B: Rename operation.

The COUNT function in SQL is used to return the number of values within a specified column. It counts the total number of rows in a result-set or the number of non-NULL values in a specific column. Here's an explanation of each option:

Option A: values.
This is the correct answer. The COUNT function counts the total number of values (or rows) in a result-set or a specific column.

Option B: distinct values.
The COUNT function can also be used with the DISTINCT keyword to count the number of distinct (unique) values in a column. However, this is not the primary function of the COUNT function.

Option C: groups.
The COUNT function is not used to count groups. It is primarily used for counting values or rows.

Option D: columns.
The COUNT function does not count columns. It counts the number of values or rows.

So, the correct answer is Option A: values..

All of the options provided (CHARACTER, NUMERIC, and FLOAT) are valid SQL data types:

CHARACTER represents character strings or text.
NUMERIC represents numeric values like integers and decimals.
FLOAT represents floating-point numbers.

So, the correct answer is Option D: All of the above.

NULL in SQL is used to represent missing or unknown data. It is not the same as 0 for integer or blank for character. In fact, NULL is not a specific value, but rather an absence of a value or a placeholder for missing data.

So, the correct answer is Option D: not a value.