Perform database query operations (create, update, delete)

10 Database and File Concepts – Query Operations

Create (INSERT) 📥

Imagine you’re adding a new student to a class roster. In a database, you do the same with an INSERT statement.

  1. Choose the table (e.g., students).
  2. Specify the columns you’re adding data to.
  3. Provide the values for each column.
  4. Execute the statement.
SQL Syntax Example
INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...); INSERT INTO students (id, name, age) VALUES (101, 'Alice', 15);
Exam Tip: Remember that INSERT can also be used with SELECT to copy rows from one table to another. Practice writing both simple and multi-row inserts.

Update (UPDATE) ✏️

Updating is like correcting a typo in a student’s phone number. Use UPDATE to modify existing data.

  1. Select the table to update.
  2. Define the new values with SET.
  3. Specify which rows to change with WHERE (never forget the WHERE clause unless you want to change everything!).
  4. Execute the statement.
SQL Syntax Example
UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition; UPDATE students SET age = 16 WHERE id = 101;
Exam Tip: Practice writing UPDATE statements that change multiple columns at once and use complex WHERE conditions (e.g., WHERE age > 15 AND name LIKE 'A%').

Delete (DELETE) 🗑️

Deleting is like removing a student who has left the school. Use DELETE to remove rows.

  1. Select the table from which to delete.
  2. Specify the rows to remove with WHERE (again, never forget it!).
  3. Execute the statement.
SQL Syntax Example
DELETE FROM table_name WHERE condition; DELETE FROM students WHERE id = 101;
Exam Tip: When writing DELETE statements, double‑check the WHERE clause. A missing clause will delete all rows in the table!

Quick Reference Cheat‑Sheet

Operation Key Clause Remember
INSERT VALUES Always list columns in the same order as values.
UPDATE SET Never omit WHERE unless you mean to update all rows.
DELETE WHERE Missing WHERE deletes everything – a common exam trap.
Final Exam Reminder: Practice writing full INSERT, UPDATE, and DELETE statements from scratch. Pay special attention to syntax, punctuation, and the WHERE clause. Good luck! 🚀

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