From c8ad7c53f34a6e005eaa7cbb8f45ae4798301dac Mon Sep 17 00:00:00 2001
From: Hau Nguyen <hauvipapro@gmail.com>
Date: Sun, 12 Jan 2025 00:16:36 +0700
Subject: [PATCH] true false unknown logic

---
 docs/2022-07-31-sql.html | 1 +
 posts/2022-07-31-sql.md  | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/docs/2022-07-31-sql.html b/docs/2022-07-31-sql.html
index cf6452e..87e4aa7 100644
--- a/docs/2022-07-31-sql.html
+++ b/docs/2022-07-31-sql.html
@@ -288,6 +288,7 @@
       <code>NULL != NULL</code>, we only can check with <code>IS NULL</code> or
       <code>IS NOT NULL</code>.
     </p>
+    <p>This is based on Kleene's TRUE-FALSE-UNKNOWN logic.</p>
     <div class="markdown-heading">
       <h2 class="heading-element"><code>VARCHAR</code> or <code>TEXT</code></h2>
       <a
diff --git a/posts/2022-07-31-sql.md b/posts/2022-07-31-sql.md
index db97f2a..bcad768 100644
--- a/posts/2022-07-31-sql.md
+++ b/posts/2022-07-31-sql.md
@@ -134,6 +134,8 @@ WHERE (field_something IS NULL OR field_something != 1)
 Because `NULL` is not equal to anything, even `NULL != NULL`, we only can check
 with `IS NULL` or `IS NOT NULL`.
 
+This is based on Kleene's TRUE-FALSE-UNKNOWN logic.
+
 ## `VARCHAR` or `TEXT`
 
 Prefer `VARCHAR` if you need to query and of course use index, and make sure