Introduction to DBMS and MySQL

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Questions and Answers

Explain the difference between DDL and DML commands in MySQL, providing an example of each.

DDL commands are used to define the database schema, such as creating, altering, or dropping tables. An example is CREATE TABLE. DML commands are used to manage data within the database, such as inserting, updating, or deleting records. An example is INSERT INTO.

Describe a scenario where using the `BETWEEN` operator in a MySQL query would be more efficient than using multiple comparison operators.

When filtering records based on a range. For example, selecting all orders with a total value between $100 and $500 can be simplified using WHERE total_value BETWEEN 100 AND 500 instead of WHERE total_value >= 100 AND total_value <= 500.

How can aggregate functions like `AVG` and `COUNT` be used together in a MySQL query to analyze data?

You can use AVG and COUNT to get the average value of something and how many entries were used to calculate that average. SELECT AVG(salary), COUNT(*) FROM employees WHERE department = 'Sales'; This will calculate the average salary of employees in the Sales department and also count the number of employees.

Explain how to modify a column's data type in an existing MySQL table.

You can change a column's data type using the <code>ALTER TABLE</code> statement, use <code>MODIFY COLUMN</code> to rename the column. For example, <code>ALTER TABLE employees MODIFY COLUMN employee_id VARCHAR(10);</code> Signup and view all the answers

Describe how the `WHERE` clause is pivotal in MySQL queries for data retrieval and manipulation.

The <code>WHERE</code> clause filters records, ensuring only relevant data is retrieved or modified. Without it, <code>SELECT</code> statements would return all rows, and <code>UPDATE</code> or <code>DELETE</code> statements would affect all records in a table. Signup and view all the answers

Outline the steps to create a new database and a table within that database using MySQL Workbench.

First, connect to your MySQL server in Workbench. Use the <code>CREATE DATABASE</code> command followed by the database name. Then, select the newly created database using the <code>USE</code> command. Finally, define your table structure with column names and data types using the <code>CREATE TABLE</code> statement. Signup and view all the answers

Explain the use case for the `LIKE` operator in MySQL and provide an example.

The <code>LIKE</code> operator is used for pattern matching in <code>WHERE</code> clauses. For example, <code>SELECT * FROM products WHERE product_name LIKE 'Laptop%';</code> retrieves all products with names starting with 'Laptop'. Signup and view all the answers

Describe what data types MySQL supports.

MySQL supports strings (<code>VARCHAR</code>, <code>TEXT</code>, etc.), numerics (<code>INT</code>, <code>DECIMAL</code>, <code>FLOAT</code>, etc.), date and time (<code>DATE</code>, <code>DATETIME</code>, <code>TIMESTAMP</code>, etc.). Signup and view all the answers

Explain the purpose of using `IS NULL` in a `WHERE` clause and provide a scenario.

<code>IS NULL</code> checks for missing or unknown values in a column. For example, <code>SELECT * FROM customers WHERE phone_number IS NULL;</code> retrieves all customers who have not provided a phone number. Signup and view all the answers

Explain the difference between `DROP TABLE` and `DELETE FROM` table commands in MySQL.

<code>DROP TABLE</code> removes the entire table including structure from the database. <code>DELETE FROM</code> removes all records from the table, but the table structure remains. Signup and view all the answers

Flashcards

MySQL Data Types

Numeric, Date and Time, String.

MySQL Operators

Arithmetic, Comparison, Logical.