ORDER BY single column in MySQL - Step-by-Step Execution

Concept Flow - ORDER BY single column

Start Query

↓

Fetch Rows from Table

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Sort Rows by Column

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Return Sorted Rows

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End Query

The query fetches all rows, sorts them by one column, then returns the sorted list.

Execution Sample

MySQL

SELECT name, age FROM users ORDER BY age;

This query selects names and ages from users and sorts the results by age in ascending order.

Execution Table

Step	Action	Data State	Result
1	Fetch all rows from users	[{name: 'Alice', age: 30}, {name: 'Bob', age: 25}, {name: 'Carol', age: 35}]	All rows fetched unsorted
2	Sort rows by age ascending	[{name: 'Bob', age: 25}, {name: 'Alice', age: 30}, {name: 'Carol', age: 35}]	Rows sorted by age
3	Return sorted rows	[{name: 'Bob', age: 25}, {name: 'Alice', age: 30}, {name: 'Carol', age: 35}]	Query result returned
4	End query	N/A	Execution complete

💡 All rows sorted by age ascending, query ends

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
rows	empty	[{name: 'Alice', age: 30}, {name: 'Bob', age: 25}, {name: 'Carol', age: 35}]	[{name: 'Bob', age: 25}, {name: 'Alice', age: 30}, {name: 'Carol', age: 35}]	[{name: 'Bob', age: 25}, {name: 'Alice', age: 30}, {name: 'Carol', age: 35}]

Key Moments - 2 Insights

Why does the order of rows change after step 2?

Because the ORDER BY clause sorts the rows by the specified column (age), changing their order from the original fetch.

What if two rows have the same age? How does ORDER BY handle that?

Rows with the same age keep their relative order from the original fetch (stable sort), unless another column is specified for sorting.

Visual Quiz - 3 Questions

Look at the execution table, what is the order of rows after step 2?

A [{Bob,25}, {Alice,30}, {Carol,35}]

B [{Alice,30}, {Bob,25}, {Carol,35}]

C [{Carol,35}, {Alice,30}, {Bob,25}]

D [{Bob,25}, {Carol,35}, {Alice,30}]

💡 Hint

Check the 'Data State' column in step 2 of the execution table.

At which step does the query return the sorted rows?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the step where 'Return sorted rows' is the action.

If we change ORDER BY age to ORDER BY age DESC, how would the order after step 2 change?

A [{Bob,25}, {Alice,30}, {Carol,35}]

B [{Carol,35}, {Alice,30}, {Bob,25}]

C [{Alice,30}, {Bob,25}, {Carol,35}]

D [{Carol,35}, {Bob,25}, {Alice,30}]

💡 Hint

Descending order means highest age first; check the sorted list in step 2.

Concept Snapshot

ORDER BY single column:
- Syntax: SELECT columns FROM table ORDER BY column_name;
- Sorts rows by one column in ascending order by default.
- Use DESC for descending order.
- Returns all rows sorted by that column.
- Sorting happens after fetching rows.

Full Transcript

This visual execution shows how a SQL query with ORDER BY on a single column works. First, all rows are fetched from the table. Then, the rows are sorted by the specified column in ascending order by default. Finally, the sorted rows are returned as the query result. The variable 'rows' changes from unsorted to sorted after the ORDER BY step. This helps beginners see how the sorting affects the data step-by-step.