IF-ELSE in procedures in SQL - Step-by-Step Execution

Concept Flow - IF-ELSE in procedures

Start Procedure

↓

Evaluate IF condition

↓

Execute IF block

↓

End Procedure

The procedure starts, checks the IF condition, executes the IF block if true, otherwise executes the ELSE block, then ends.

Execution Sample

SQL

CREATE PROCEDURE CheckAge(IN age INT)
BEGIN
  IF age >= 18 THEN
    SELECT 'Adult';
  ELSE
    SELECT 'Minor';
  END IF;
END;

This procedure checks if the input age is 18 or older and returns 'Adult' or 'Minor' accordingly.

Execution Table

Step	Input age	Condition (age >= 18)	Branch Taken	Output
1	20	True	IF block	'Adult'
2	17	False	ELSE block	'Minor'
3	18	True	IF block	'Adult'
4	0	False	ELSE block	'Minor'
5	Exit	-	-	Procedure ends

💡 Procedure ends after executing IF or ELSE block based on condition.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
age	undefined	20	17	18	0	-
condition (age >= 18)	undefined	True	False	True	False	-
output	undefined	'Adult'	'Minor'	'Adult'	'Minor'	-

Key Moments - 2 Insights

Why does the ELSE block run when age is 17?

Because the condition age >= 18 is False at step 2 in the execution_table, so the ELSE block executes.

What happens if age is exactly 18?

At step 3, the condition age >= 18 is True, so the IF block runs and outputs 'Adult'.

Visual Quiz - 3 Questions

Look at the execution_table, what output is produced when age is 20?

A No output

B 'Minor'

C 'Adult'

D Error

💡 Hint

Check row 1 in execution_table where age=20 and output is shown.

At which step does the condition become False?

A Step 2

B Step 1

C Step 3

D Step 5

💡 Hint

Look at the 'Condition' column in execution_table for False values.

If age is changed to 15, which branch will execute?

A IF block

B ELSE block

C Both IF and ELSE blocks

D Neither block

💡 Hint

Refer to variable_tracker and execution_table where condition is False for ages less than 18.

Concept Snapshot

IF-ELSE in SQL procedures:
- Use IF condition THEN ... ELSE ... END IF;
- Condition is evaluated once per call
- IF block runs if condition True
- ELSE block runs if condition False
- Helps control flow inside procedures

Full Transcript

This visual execution trace shows how IF-ELSE works inside SQL procedures. The procedure starts and checks the condition age >= 18. If true, it runs the IF block and outputs 'Adult'. If false, it runs the ELSE block and outputs 'Minor'. The execution table shows different input ages and which branch runs. The variable tracker follows the age input, condition result, and output at each step. Key moments clarify why ELSE runs for age 17 and IF runs for age 18. The quiz tests understanding of outputs and condition results. This helps beginners see step-by-step how IF-ELSE controls procedure flow.