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true false unknown logic

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sudo pacman -Syu 2025-01-12 00:16:36 +07:00
parent 0c7cefa467
commit c8ad7c53f3
2 changed files with 3 additions and 0 deletions
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docs/2022-07-31-sql.html
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@ -288,6 +288,7 @@
<code>NULL != NULL</code>, we only can check with <code>IS NULL</code> or <code>NULL != NULL</code>, we only can check with <code>IS NULL</code> or
<code>IS NOT NULL</code>. <code>IS NOT NULL</code>.
</p> </p>
<p>This is based on Kleene's TRUE-FALSE-UNKNOWN logic.</p>
<div class="markdown-heading"> <div class="markdown-heading">
<h2 class="heading-element"><code>VARCHAR</code> or <code>TEXT</code></h2> <h2 class="heading-element"><code>VARCHAR</code> or <code>TEXT</code></h2>
<a <a

2
posts/2022-07-31-sql.md
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@ -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 Because `NULL` is not equal to anything, even `NULL != NULL`, we only can check
with `IS NULL` or `IS NOT NULL`. with `IS NULL` or `IS NOT NULL`.
This is based on Kleene's TRUE-FALSE-UNKNOWN logic.
## `VARCHAR` or `TEXT` ## `VARCHAR` or `TEXT`
Prefer `VARCHAR` if you need to query and of course use index, and make sure Prefer `VARCHAR` if you need to query and of course use index, and make sure