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feat: add explain mysql

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sudo pacman -Syu 2023-04-17 17:14:54 +07:00
parent 5e4a593acf
commit 9b5fceacaf
2 changed files with 30 additions and 0 deletions
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24
docs/2022-07-31-sql.html
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@ -131,6 +131,23 @@
<pre><span class="pl-k">CREATE</span> <span class="pl-k">INDEX</span> `<span class="pl-en">idx_timestamp</span>` <pre><span class="pl-k">CREATE</span> <span class="pl-k">INDEX</span> `<span class="pl-en">idx_timestamp</span>`
<span class="pl-k">ON</span> <span class="pl-s"><span class="pl-pds">`</span>user_upload<span class="pl-pds">`</span></span> (<span class="pl-s"><span class="pl-pds">`</span>timestamp<span class="pl-pds">`</span></span>);</pre> <span class="pl-k">ON</span> <span class="pl-s"><span class="pl-pds">`</span>user_upload<span class="pl-pds">`</span></span> (<span class="pl-s"><span class="pl-pds">`</span>timestamp<span class="pl-pds">`</span></span>);</pre>
</div> </div>
<p>Use <code>EXPLAIN</code> to check if index is used or not:</p>
<ul>
<li>
<a
href="https://dev.mysql.com/doc/refman/5.7/en/explain-output.html"
rel="nofollow"
>For MySQL 5.7</a
>
</li>
<li>
<a
href="https://dev.mysql.com/doc/refman/8.0/en/explain-output.html"
rel="nofollow"
>For MySQL 8.0</a
>
</li>
</ul>
<h2> <h2>
<a <a
id="user-content-be-careful-with-null" id="user-content-be-careful-with-null"
@ -273,6 +290,13 @@
>My Notes on GitLab Postgres Schema Design</a >My Notes on GitLab Postgres Schema Design</a
> >
</li> </li>
<li>
<a
href="https://planetscale.com/blog/how-read-mysql-explains"
rel="nofollow"
>How to read MySQL EXPLAINs</a
>
</li>
</ul> </ul>
<div> <div>

6
posts/2022-07-31-sql.md
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@ -53,6 +53,11 @@ CREATE INDEX `idx_timestamp`
ON `user_upload` (`timestamp`); ON `user_upload` (`timestamp`);
``` ```
Use `EXPLAIN` to check if index is used or not:
- [For MySQL 5.7](https://dev.mysql.com/doc/refman/5.7/en/explain-output.html)
- [For MySQL 8.0](https://dev.mysql.com/doc/refman/8.0/en/explain-output.html)
## Be careful with NULL ## Be careful with NULL
If compare with field which can be NULL, remember to check NULL for safety. If compare with field which can be NULL, remember to check NULL for safety.
@ -97,3 +102,4 @@ Plase read docs about online ddl operations before do anything online (keep data
- [Things You Should Know About Databases](https://architecturenotes.co/things-you-should-know-about-databases/) - [Things You Should Know About Databases](https://architecturenotes.co/things-you-should-know-about-databases/)
- [When to use JSON data type in database schema design?](https://shekhargulati.com/2022/01/08/when-to-use-json-data-type-in-database-schema-design/) - [When to use JSON data type in database schema design?](https://shekhargulati.com/2022/01/08/when-to-use-json-data-type-in-database-schema-design/)
- [My Notes on GitLab Postgres Schema Design](https://shekhargulati.com/2022/07/08/my-notes-on-gitlabs-postgres-schema-design/) - [My Notes on GitLab Postgres Schema Design](https://shekhargulati.com/2022/07/08/my-notes-on-gitlabs-postgres-schema-design/)
- [How to read MySQL EXPLAINs](https://planetscale.com/blog/how-read-mysql-explains)