RAISE for notices and exceptions in PostgreSQL - Step-by-Step Execution

Concept Flow - RAISE for notices and exceptions

Start PL/pgSQL block

↓

Execute statements

↓

RAISE statement encountered?

No→Continue execution

Yes↓

Check RAISE level: NOTICE, WARNING, EXCEPTION

↓

NOTICE/WARNING: Show message, continue

↓

EXCEPTION: Show error, stop execution

↓

End block or handle exception

The flow shows how a RAISE statement in PostgreSQL PL/pgSQL triggers messages or errors, either continuing or stopping execution.

Execution Sample

PostgreSQL

DO $$
BEGIN
  RAISE NOTICE 'Step 1: Starting';
  IF TRUE THEN
    RAISE EXCEPTION 'Error occurred';
  END IF;
END $$;

This code raises a notice message, then raises an exception which stops execution.

Execution Table

Step	Action	RAISE Level	Message	Execution Continues?
1	Start block	N/A	N/A	Yes
2	RAISE NOTICE 'Step 1: Starting'	NOTICE	Step 1: Starting	Yes
3	Check IF condition TRUE	N/A	N/A	Yes
4	RAISE EXCEPTION 'Error occurred'	EXCEPTION	Error occurred	No
5	Block ends due to exception	N/A	N/A	No

💡 Execution stops at step 4 due to RAISE EXCEPTION.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
Execution State	Not started	Notice shown	Condition checked	Exception raised	Stopped

Key Moments - 2 Insights

Why does execution stop after RAISE EXCEPTION but not after RAISE NOTICE?

RAISE NOTICE only shows a message and lets execution continue (see step 2 and 5 in execution_table). RAISE EXCEPTION raises an error that stops execution immediately (step 4).

Can RAISE WARNING stop execution like EXCEPTION?

No, RAISE WARNING behaves like NOTICE by showing a message but continuing execution. Only EXCEPTION stops execution as shown in step 4.

Visual Quiz - 3 Questions

Look at the execution_table, what message is shown at step 2?

A Error occurred

B Step 1: Starting

C Condition checked

D Block ends

💡 Hint

Check the 'Message' column at step 2 in execution_table.

At which step does execution stop due to an error?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the 'Execution Continues?' column in execution_table.

If we replace RAISE EXCEPTION with RAISE WARNING at step 4, what changes?

A No message is shown

B Execution stops earlier

C Execution continues after step 4

D An error is raised

💡 Hint

RAISE WARNING behaves like NOTICE and does not stop execution (see explanation in key_moments).

Concept Snapshot

RAISE statement syntax:
RAISE level 'message';
Levels: NOTICE, WARNING, EXCEPTION
NOTICE and WARNING show messages and continue execution.
EXCEPTION raises error and stops execution.
Use RAISE to debug or handle errors in PL/pgSQL.

Full Transcript

This visual execution trace shows how the RAISE statement works in PostgreSQL PL/pgSQL. When the block starts, it executes normally. At step 2, RAISE NOTICE outputs a message but lets execution continue. At step 4, RAISE EXCEPTION raises an error message and stops the block immediately. The variable tracker shows the execution state changing from started to stopped after the exception. Key moments clarify that only EXCEPTION stops execution, while NOTICE and WARNING do not. The quiz tests understanding of message output and execution flow. The snapshot summarizes syntax and behavior of RAISE levels.