Write any two differences between UPDATE and ALTER TABLE commands of MySQL.

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Q. Write any two differences between UPDATE and ALTER TABLE commands of MySQL.

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Concept understanding — SQL Query Concepts

SQL Query Concepts — A First Look

Think of a library. You walk in, and instead of wandering through endless shelves, you go to the librarian and say: "Give me all the books by Tagore published after 1950, sorted by title." The librarian knows exactly where everything is, finds what you asked for, and hands you the list. That's what SQL does — but for data stored in a computer.

SQL stands for Structured Query Language. It is the language we use to talk to databases. A database is just a collection of related information stored in tables — like an Excel workbook with multiple sheets, but far more powerful and organised.

The core idea: tables and queries

A database stores data in tables. Each table has rows (records) and columns (fields). For example, a Students table might have columns like RollNo, Name, City, and Marks. Each row is one student's complete information.

A query is simply a question you ask the database. You write it in SQL, and the database returns an answer — usually a new table made from the data that matches your question.

Note

SQL is not a programming language like Python or Java. You don't tell the computer how to find the data. You only say what data you want. The database figures out the fastest way to get it.

The most common SQL command: SELECT

Almost every query begins with SELECT. It means "show me this data." The basic structure is:

SELECT column1, column2 FROM table_name WHERE condition;

Read it like a sentence: "Select these columns from this table where this condition is true."

If you want all columns, you write SELECT *. The asterisk is a shortcut meaning "everything."

Filtering with WHERE

The WHERE clause is your filter. It keeps only the rows that satisfy a condition. For example, if you want students from Delhi only, you write:

SELECT * FROM Students WHERE City = 'Delhi';

You can combine conditions using AND (both must be true) and OR (at least one must be true). This is exactly like everyday logic: "Show me students from Delhi AND who scored above 80."

Sorting with ORDER BY

Data often comes back in no particular order. To arrange it, use ORDER BY. You can sort ascending (smallest first, which is the default) or descending (largest first) using DESC.

SELECT Name, Marks FROM Students ORDER BY Marks DESC;

This gives you a ranked list — highest marks first.

Why SQL matters for commerce and humanities

You will never calculate a formula in SQL. That is not what it does. What SQL does is organise, filter, and retrieve information — and that is the foundation of every data-driven decision. …

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The key idea is understanding the distinct roles of Data Manipulation Language (DML) and Data Definition Language (DDL) commands in SQL. UPDATE is a DML command, while ALTER TABLE is a DDL command, each serving a fundamentally different purpose in database management.

Here are two differences:

Purpose of Modification: UPDATE is used to modify the data (rows/records) within an existing table, changing values in one or more columns. In contrast, ALTER TABLE is used to modify the structure (schema/definition) of an existing table, such as adding, dropping, or modifying columns, or adding/removing constraints. …

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UPDATE modifies existing data within a table's rows, while ALTER TABLE modifies the table's structure or schema itself.

In MySQL, understanding the distinction between UPDATE and ALTER TABLE commands is fundamental to managing your database effectively. These commands serve entirely different purposes, even though both involve "changing" something related to a table. The key lies in what aspect of the table they are designed to change: its contents or its definition.

UPDATE is part of the Data Manipulation Language (DML). Its role is to modify the actual values stored in one or more rows and columns of an existing table. Think of it like editing the content inside a spreadsheet cell. You're not changing the number of columns, or the column headers, but the data within them.

ALTER TABLE, on the other hand, belongs to the Data Definition Language (DDL). Its purpose is to change the structure or schema of a table. This means you're modifying the table's blueprint: adding new columns, removing existing ones, changing data types, adding constraints, or renaming the table itself. It's like adding a new column to your spreadsheet, or changing a column from expecting numbers to expecting text.

Here are two key differences between UPDATE and ALTER TABLE commands:

Purpose and Scope:
- UPDATE: This command is used to modify the data stored in the rows of a table. It operates on the contents of the table. You specify which rows to update using a WHERE clause, and which columns to change using the SET clause.
  - Example: Changing a student's grade from 'A' to 'A+' in the students table.
  - UPDATE students SET grade = 'A+' WHERE student_id = 101;
- ALTER TABLE: This command is used to modify the structure or schema of a table. It operates on the definition of the table itself, not its data. This includes adding, dropping, or modifying columns, adding or dropping constraints (like primary keys, foreign keys, unique constraints), or renaming the table.
  - Example: Adding a new column email to the students table.
  - ALTER TABLE students ADD COLUMN email VARCHAR(255);
SQL Command Type (DML vs. DDL): …

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Q.Write any two differences between UPDATE and ALTER TABLE commands of MySQL.

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