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Easy
Basic SELECT Query
Filtering Data with WHERE Clauses
Sorting Data with ORDER BY
Using Aggregate Functions
Grouping Data with GROUP BY
Filtering Groups with HAVING
Joining Tables (INNER JOIN)
LEFT JOIN and NULL Handling
Combining Results with UNION
Medium
Subqueries for Complex Filtering
Using CASE Statements
Basic SELECT Query
  • Description: Learn the fundamentals of retrieving data from a single table using SELECT statements. The task is to select all records from the employees table.
  • Table Used: employees
    • Columns: employee_id, first_name, last_name, department, salary
  • Expected Columns Returned: employee_id, first_name, last_name, department
  • Schema:
classDiagram direction BT class Employees { integer employee_id text first_name text last_name text department float salary }

select * from employees