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DATA MANIPULATION

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1. Which of the following languages is used in application programs, to retrieve, store, modify, delete, insert and update data in database?

1. DML 2. DDL 3. DCL 4. TCL Answer: DML Concept: A data manipulation language (DML) is a computer programming language used for adding (inserting), deleting, and modifying (updating) data in a database. A DML is often a sublanguage of a broader database language such as SQL, with the DML comprising some of the operators in the language.

Hence the correct answer is DML Visit: www.matlabassignmentexperts.com Email: Info@matlabassignmentexperts.com WhatsApp: +1(315)557-6473

2. What is the highest level of data abstraction in the database management system?

1. Physical level 2. Logical Level 3. View Level 4. Hashing 5. None of these Answer: View Level Key Points Database systems comprise complex data-structures. In order to make the system efficient in terms of retrieval of data, and reduce complexity in terms of usability of users, developers use abstraction i.e. hide irrelevant details from the users. This approach simplifies database design.

There are mainly 3 levels of data abstraction: 1. Physical: This is the lowest level of data abstraction. It tells us how the data is actually stored in memory. The access methods like sequential or random access and file organization methods like B+ trees, hashing used for the same. Usability, size of memory, and the number of times the records are factors that we need to know while designing the database. Suppose we need to store the details of an employee. Blocks of storage and the amount of memory used for these purposes are kept hidden from the user.

2. Logical: This level comprises the information that is actually stored in the database in the form of tables. It also stores the relationship among the data entities in relatively simple Visit: www.matlabassignmentexperts.com Email: Info@matlabassignmentexperts.com WhatsApp: +1(315)557-6473

structures. At this level, the information available to the user at the view level is unknown. We can store the various attributes of an employee and relationships, e.g. with the manager can also be stored.

3. View: This is the highest level of abstraction. Only a part of the actual database is viewed by the users. This level exists to ease the accessibility of the database by an individual user. Users view data in the form of rows and columns. Tables and relations are used to store data. Multiple views of the same database may exist. Users can just view the data and interact with the database, storage and implementation details are hidden from them.

View 1

View 2

View 3

Logical Level

Physical Level

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3. ________is to express database queries and updates.

1. data definition language 2. data manipulation language 3. data control language 4. transaction control language 5. Hypertext Markup Language Answer: data manipulation language The correct answer is data manipulation language • A database system provides a data-definition language (DDL) to specify the database schema Example of DDL commands: CREATE, DROP etc.

• A data-manipulation language (DML) is a language that enables users to access or manipulate data as organized by the appropriate model Example of DML commands: INSERT, DELETE etc.

• A data control language (DCL) is used to control access (Authorization) to data stored in a database Example of DCL commands: GRANT and REVOKE • A transaction control language (TCL) is used to control transactional processing in a database Example of TCL commands: COMMIT, SAVEPOINT etc 4. Which of the following SQL commands are used to delete a table from a database?

1. Purge 2. Truncate 3. Delete 4. Drop Visit: www.matlabassignmentexperts.com Email: Info@matlabassignmentexperts.com WhatsApp: +1(315)557-6473

Answer: Drop Key Points • DROP - It is a Data Definition Language (DDL) Command which is used to delete, tables, views, triggers, etc from a database.

• A DROP statement in SQL removes a component from a relational database management system (RDBMS).

Additional Information • Data Definition Language (DDL) - Data Definition Language consists of SQL commands that can be used to define the database.

• List of DDL commands

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5. Which of the following operation(s) will manipulate data in MySQL? 1. Delete 2. Update 3. Insert 4. Merge 5. All of the above Answer: All of the above Data-manipulation language (DML).

It is a language that enables users to access or manipulate data as organized by the appropriate model.

Example of DML commands: INSERT, DELETE, UPDATE, MERGE, SELECT etc.

Explanation: • Delete will delete the tuples from the relation (table) • Update will change the value of particular cell in a relation.

• Insert will insert the tuples from the relation. Therefore delete, update and insert are update operation in SQL • Merge - UPSERT operation (insert or update) • Hence all the operation will update in MySQL

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