From c8a05feb95290c16e5b649c3dacb7f373367d5b2 Mon Sep 17 00:00:00 2001
From: Matthew Huntington <matt.huntington@gmail.com>
Date: Thu, 19 Oct 2023 23:03:06 -0400
Subject: [PATCH] locks

---
 SQL/lessons/sql_3.md | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/SQL/lessons/sql_3.md b/SQL/lessons/sql_3.md
index d2aca79..5f3705d 100644
--- a/SQL/lessons/sql_3.md
+++ b/SQL/lessons/sql_3.md
@@ -215,6 +215,19 @@ SELECT * FROM people;
 
 ### Locks
 
+```sql
+BEGIN;
+LOCK TABLE people IN ROW EXCLUSIVE MODE;
+SELECT * FROM people WHERE id = 12 FOR UPDATE;
+
+-- start a new session and run UPDATE people SET name = 'Matt' WHERE id = 12;
+-- switch back to original session
+
+UPDATE people SET age = 43 WHERE id = 12;
+SELECT * FROM people;
+END;
+```
+
 ### Privileges
 
 ### Denormalization