SQL Q&A
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- What is a database?
A structured collection of data stored and accessed electronically. - What is a DBMS?
Database Management System; software that interacts with databases to manage data. - What is SQL?
Structured Query Language; a standard language for managing and manipulating databases. - What is a primary key?
A unique identifier for a record in a table. - What is a foreign key?
A field that links to the primary key of another table, establishing a relationship. - What are the main data types in MySQL?
Numeric (INT, DECIMAL), String (VARCHAR, TEXT), Date/Time (DATE, TIMESTAMP). - What is the difference between CHAR and VARCHAR?
CHAR is fixed-length; VARCHAR is variable-length, saving space. - What is a NULL value?
A value that represents the absence of data. - What is a default value?
A value automatically assigned to a column when no value is specified. - What is a composite key?
A key that consists of two or more columns used to uniquely identify a record. - What is a SELECT statement?
A SQL command used to retrieve data from a database. - How do you filter records in SQL?
Using the WHERE clause. - What is an INNER JOIN?
A join that returns rows with matching values in both tables. - What is a LEFT JOIN?
A join that returns all rows from the left table and matching rows from the right table. - What is GROUP BY used for?
To group rows that have the same values in specified columns. - What is an index?
A database structure that improves the speed of data retrieval operations. - What is the difference between clustered and non-clustered index?
A clustered index sorts and stores data rows, while a non-clustered index is a separate structure that references data rows. - What are the advantages of using indexes?
Faster search and retrieval times for data. - What are the disadvantages of using indexes?
Increased storage space and slower write operations (insert/update). - What is a full-text index?
An index that allows for full-text searches on string columns. - What is a transaction?
A sequence of one or more SQL operations treated as a single unit. - What are the ACID properties?
Atomicity, Consistency, Isolation, Durability; they ensure reliable transactions. - What is a rollback?
A command that undoes changes made in the current transaction. - What is a commit?
A command that saves all changes made during the current transaction. - What is a savepoint?
A point within a transaction to which you can later roll back. - What is normalization?
The process of organizing data to minimize redundancy and dependency. - What are normal forms?
Guidelines (1NF, 2NF, 3NF, etc.) for structuring databases to reduce redundancy. - What is denormalization?
The process of combining tables to improve read performance at the cost of redundancy. - What is 1NF?
First Normal Form; ensures that each column contains atomic values and each entry is unique. - What is 2NF?
Second Normal Form; removes partial dependencies on a composite primary key. - What is SQL injection?
A security vulnerability that allows an attacker to interfere with the queries an application makes to a database. - How can you prevent SQL injection?
Use prepared statements and parameterized queries. - What is user authentication?
Verifying the identity of a user accessing the database. - What is data encryption?
The process of converting data into a code to prevent unauthorized access. - What is a stored procedure?
A precompiled collection of SQL statements stored in the database. - What is a database backup?
A copy of the database that can be used to restore it in case of data loss. - What is a trigger?
A set of instructions that automatically executes in response to certain events on a table. - What is a view?
A virtual table based on the result of a SQL query. - What are stored functions?
Functions that are stored in the database and can be called from SQL statements. - What is a data warehouse?
A centralized repository for storing and analyzing large volumes of data. - What is partitioning?
Dividing a large database table into smaller, more manageable pieces. - What is a NoSQL database?
A non-relational database that provides flexible data models for unstructured data.
