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Database / SQL Basics

Reasoning & Computer Aptitude · Office, Database & Networking

Useful for: IBPS Banking

Overview

A database stores related data in tables; SQL is the language used to define, query and change it.

Key points

DBMS manages databases; RDBMS stores data in related tables.
Primary key uniquely identifies each row; foreign key links to another table’s primary key.
DDL: CREATE, ALTER, DROP; DML: SELECT, INSERT, UPDATE, DELETE; DCL: GRANT, REVOKE.
DELETE removes rows; DROP removes the whole table.
Normalisation reduces redundancy.

Explanation

A row is also called a record or tuple; a column a field or attribute.
WHERE filters rows; ORDER BY sorts results.
Banks use databases for accounts, transactions and customer records.
Backups protect databases from loss.

Step by step

Identify the term or device asked.
Recall its definition or function.
Eliminate options from other categories.

Examples

The key that links two tables → foreign key.
The SQL command that removes an entire table → DROP.
SELECT belongs to → DML.

Traps and advanced points

Trap: Mixing DELETE and DROP.
Trap: Calling a column a record.
Trap: Thinking a primary key can repeat.

Quick revision

PK unique; FK links.
DDL/DML/DCL.
DELETE rows, DROP table.

Practice MCQs

Computer awareness: “SQL” is best matched with:
1. Structured Query Language
2. service that indexes/retrieves web information
3. transforming data using a key to protect confidentiality
4. Uniform Resource Locator
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Answer: (a) Structured Query Language. SQL” is best matched with Structured Query Language.
Computer awareness: “DBMS” is best matched with:
1. Arithmetic Logic Unit
2. Database Management System
3. transforming data using a key to protect confidentiality
4. Comma-Separated Values
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Answer: (b) Database Management System. DBMS” is best matched with Database Management System.
A primary key —
1. uniquely identifies each row
2. links to another table only
3. stores images
4. deletes data
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Answer: (a) uniquely identifies each row. Unique identifier.
A foreign key —
1. links to another table’s primary key
2. is always unique
3. deletes rows
4. is a password
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Answer: (a) links to another table’s primary key. Relationship.
Which is a DDL command?
1. SELECT
2. CREATE
3. INSERT
4. UPDATE
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Answer: (b) CREATE. Also ALTER, DROP.
Which is a DML command?
1. DROP
2. SELECT
3. GRANT
4. CREATE
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Answer: (b) SELECT. Also INSERT, UPDATE, DELETE.
Which is a DCL command?
1. INSERT
2. GRANT
3. SELECT
4. ALTER
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Answer: (b) GRANT. Also REVOKE.
DELETE removes —
1. the database
2. columns only
3. rows
4. the whole table structure
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Answer: (c) rows. Rows.
RDBMS stores data in —
1. related tables
2. one text file
3. images
4. folders only
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Answer: (a) related tables. Tables.
Normalisation mainly reduces —
1. size of keys
2. redundancy
3. speed
4. security
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Answer: (b) redundancy. Duplication.