SQL Quiz

What is the full form of SQL?

• 1. Structured Query List

• 1. Structure Query Language

• 1. Sample Query Language

• 1. None of these.

Which of the following is not a valid SQL type?

• 1. FLOAT

• 1. NUMERIC

• 1. DECIMAL

• 1. CHARACTER

Answer explanation

DECIMAL is not a valid SQL type because it is nothing but numeric only in SQL.

NUMERIC has fixed precision, and scale numbers range from -10^38+1 to 10^38-1.

FLOAT has floating precision number ranges from -1.79E + 308 to 1.79E + 308.

CHARACTER is a fixed-width character string data type that can be up to 8000 characters.

Which of the following is not a DDL command?

• 1. TRUNCATE

• 1. ALTER

• 1. CREATE

• 1. UPDATE

Answer explanation

DDL commands are used to define the structure of the database, table, schemas, etc. It enables us to perform the operations like CREATE, DROP, ALTER, RENAME, and TRUNCATE schema objects.

An UPDATE command is used for managing the data stored in a database. It is an example of a DML command that also includes the INSERT and DELETE commands.

Which of the following are TCL commands?

• 1. COMMIT and ROLLBACK

• 1. UPDATE and TRUNCATE

• 1. SELECT and INSERT

• 1. GRANT and REVOKE

Answer explanation

TCL stands for Transaction Control Commands used for managing the changes made by DML commands like INSERT, DELETE, and UPDATE. The TCL commands are automatically committed in the database; that's why we cannot use them directly while creating tables or dropping them.

Which statement is used to delete all rows in a table without having the action logged?

• 1. DELETE

• 1. REMOVE

• 1. DROP

• 1. TRUNCATE

Answer explanation

TRUNCATE statement removes all rows in a table without logging the individual row deletions. It uses fewer system and transaction log resources, which makes its execution fast. This statement is similar to the DELETE statement without the WHERE clause.

How many Primary keys can have in a table?

• 1. Only 1

• 1. Only 2

• 1. Depends on no of Columns

• 1. Depends on DBA

Answer explanation

The primary key can consist of a single or combination of the field that uniquely identifies each record in a table. It cannot be null or empty. A table may have duplicate columns, but it can contain only one primary key.

Which datatype can store unstructured data in a column?

• 1. CHAR

• 1. RAW

• 1. NUMERIC

• 1. VARCHAR

Answer explanation

RAW datatype stores variable-length binary data that can be queried and inserted but not manipulated.

Its maximum length is 32767 bytes.

CHAR stores character data in a fixed length.

NUMERIC stores numeric values only.

VARCHAR stores variable string data in a fixed length. Its maximum length is 4000 bytes.

Which of the following is not Constraint in SQL?

• 1. Primary Key

• 1. Not Null

• 1. Check

• 1. Union

Answer explanation

Constraint specifies the rule to allow or restrict what data will be stored in a table. The PRIMARY KEY, NOT NULL, and CHECK are the constraints that specify rules for data insertion.

UNION is an operator that combines two or more results from multiple SELECT queries into a single result set.

Which data manipulation command is used to combines the records from one or more tables?

• 1. SELECT

• 1. PROJECT

• 1. JOIN

• 1. PRODUCT

Answer explanation

JOIN command is used with the SELECT statement to retrieve data from multiple tables. It must be needed whenever we want to fetch records from two or more tables.

A command that lets you change one or more field in a table is:

• 1. INSERT

• 1. MODIFY

• 1. LOOK-UP

• 1. All of the above

Answer explanation

The modify command is used to change one or more columns in the existing table. It is generally used with ALTER TABLE statement as follows.

LTER TABLE table_name MODIFY column_name column_type;