INSERT with DEFAULT values in SQL - Step-by-Step Execution

Concept Flow - INSERT with DEFAULT values

Start INSERT command

↓

Check if VALUES provided

↓

Insert given

↓

Add row to table

↓

End

When inserting a row, if no value is given for a column, SQL uses the DEFAULT value for that column.

Execution Sample

SQL

CREATE TABLE fruits (
  id INT DEFAULT 1,
  name VARCHAR(10) DEFAULT 'apple'
);

INSERT INTO fruits DEFAULT VALUES;

This creates a table with default values and inserts a row using those defaults.

Execution Table

Step	Action	Evaluation	Result
1	Start INSERT command	INSERT INTO fruits DEFAULT VALUES;	Ready to insert a new row
2	Check if VALUES provided	No explicit values given	Use DEFAULT values for all columns
3	Assign DEFAULT to id	id DEFAULT is 1	id = 1
4	Assign DEFAULT to name	name DEFAULT is 'apple'	name = 'apple'
5	Add row to table	Row to insert: (1, 'apple')	Row inserted successfully
6	End	Insertion complete	Table now has 1 row with id=1 and name='apple'

💡 No explicit values given, so DEFAULT values used for all columns

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
id	NULL	1	1	1
name	NULL	NULL	'apple'	'apple'

Key Moments - 2 Insights

Why does the INSERT work without specifying any column values?

Because the INSERT uses DEFAULT VALUES, SQL fills in all columns with their default values as shown in execution_table step 2 and 3.

What happens if a column has no DEFAULT and no value is given?

The INSERT would fail with an error because the column requires a value. Here, all columns have defaults, so it succeeds (see execution_table step 2).

Visual Quiz - 3 Questions

Look at the execution table, what value is assigned to 'name' at step 4?

A 'default'

B NULL

C 'apple'

D 1

💡 Hint

Check the 'Assign DEFAULT to name' row in the execution_table.

At which step does the row get added to the table?

A Step 5

B Step 3

C Step 2

D Step 6

💡 Hint

Look for the action 'Add row to table' in the execution_table.

If the 'id' column had no DEFAULT value, what would happen at step 3?

A id would be set to NULL

B An error would occur

C id would be set to 0

D The row would be inserted anyway

💡 Hint

Refer to key_moments about missing DEFAULT values causing errors.

Concept Snapshot

INSERT with DEFAULT values:
- Use: INSERT INTO table DEFAULT VALUES;
- Inserts one row using all columns' default values
- If no default and no value given, error occurs
- Useful for quick inserts with defaults
- Defaults defined in table schema

Full Transcript

This visual execution shows how an INSERT statement with DEFAULT VALUES works. The process starts by checking if explicit values are provided. Since none are given, SQL uses the default values defined for each column. The 'id' column gets the default 1, and the 'name' column gets 'apple'. Then the row (1, 'apple') is added to the table. The execution ends with one row inserted. If a column had no default and no value, the insert would fail. This method is useful for inserting rows quickly using predefined defaults.