SELECT all columns in SQL - Step-by-Step Execution

Concept Flow - SELECT all columns

Start Query

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Parse SELECT *

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Identify Table

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Retrieve All Columns

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Return All Rows with All Columns

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End Query

The query starts by reading SELECT * which means all columns from the specified table are retrieved and returned.

Execution Sample

SQL

SELECT * FROM employees;

This query retrieves every column and every row from the employees table.

Execution Table

Step	Action	Evaluation	Result
1	Parse query	SELECT * FROM employees	Ready to execute
2	Identify table	employees	Table found with columns: id, name, role, salary
3	Retrieve columns	* means all columns	Columns selected: id, name, role, salary
4	Fetch rows	All rows from employees	Rows fetched: 3
5	Return result	All columns and rows	Result set with 3 rows and 4 columns
6	End query	Query complete	Execution finished

💡 All rows and all columns retrieved, query execution ends.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
table	undefined	employees	employees	employees	employees
columns	undefined	undefined	id, name, role, salary	id, name, role, salary	id, name, role, salary
rows	undefined	undefined	undefined	3 rows fetched	3 rows fetched
result_set	undefined	undefined	undefined	undefined	3 rows x 4 columns

Key Moments - 2 Insights

Why does SELECT * return all columns instead of just one?

SELECT * is a shortcut that tells the database to include every column from the table, as shown in execution_table step 3 where all columns are selected.

Does SELECT * limit the number of rows returned?

No, SELECT * returns all rows by default unless a WHERE clause is added. Execution_table step 4 shows all rows are fetched.

Visual Quiz - 3 Questions

Look at the execution table, what columns are selected at step 3?

A No columns selected yet

B id, name, role, salary

C Only id and name

D Only salary

💡 Hint

Check the 'Retrieve columns' action in execution_table step 3.

At which step does the query fetch all rows from the table?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look for 'Fetch rows' action in execution_table.

If the table had 5 columns instead of 4, how would the result set change?

A It would return 5 columns

B It would still return 4 columns

C It would return only 1 column

D It would return no columns

💡 Hint

SELECT * means all columns, so adding columns increases the count in result_set.

Concept Snapshot

SELECT * syntax:
SELECT * FROM table_name;

- '*' means all columns
- Returns all rows by default
- Useful to quickly get full table data
- Can be combined with WHERE to filter rows

Full Transcript

This visual execution shows how the SQL query SELECT * FROM employees works step-by-step. First, the query is parsed and the employees table is identified. Then, the * symbol tells the database to select all columns from the table. Next, all rows are fetched from employees. Finally, the full result set with all columns and rows is returned. This helps beginners see how SELECT * retrieves complete data from a table.