yoshie
/
posts-go
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

feat: Be careful with NULL

main
sudo pacman -Syu 2022-09-07 00:10:02 +07:00
parent fd56e04621
commit c83c2bf60a
No known key found for this signature in database
GPG Key ID: D6CB5C6C567C47B0
2 changed files with 34 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
docs/2022-07-31-sql.html
View File

@ -1,3 +1,14 @@
<!doctype html><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><link rel=preconnect href=https://fonts.googleapis.com><link rel=preconnect href=https://fonts.gstatic.com crossorigin><link href="https://fonts.googleapis.com/css2?family=Recursive:wght,CASL,MONO@300..800,0..1,0..1&display=swap" rel=stylesheet><link rel=stylesheet href=styles.css><a href=index>Index</a><h1>SQL</h1><p>Previously in my fresher time, I rarely write SQL, I always use ORM to wrap SQL.<br>But time past and too much abstraction bites me.<br>So I decide to only write SQL from now, no more ORM for me.<br>But if there is any cool ORM for Go, I guess I try.<p>This guide is not kind of guide which cover all cases.<br>Just my little tricks when I work with SQL.<h1>Stay away from database timestamp</h1><p>Stay away from all kind of timestamp, timestamp of MySQL or any database.<br>Just use int64 then pass the timestamp in service layer not database layer.<p>Why? Because time and date and location are too much complex to handle.<br>In my business, I use timestamp in milliseconds.<br>Then I save timestamp as int64 value to database.<br>Each time I get timestamp from database, I parse to time struct in Go with location or format I want.<br>No more hassle!<h1>Use index</h1><p>You should use index for faster query, but not too much.<br>Don't create index for every fields in table.<br>Choose wisely!<p>For example, create index in MySQL:<pre><code class=language-sql>CREATE INDEX `idx_timestamp`
<!doctype html><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><link rel=preconnect href=https://fonts.googleapis.com><link rel=preconnect href=https://fonts.gstatic.com crossorigin><link href="https://fonts.googleapis.com/css2?family=Recursive:wght,CASL,MONO@300..800,0..1,0..1&display=swap" rel=stylesheet><link rel=stylesheet href=styles.css><a href=index>Index</a><h1>SQL</h1><p>Previously in my fresher time, I rarely write SQL, I always use ORM to wrap SQL.<br>But time past and too much abstraction bites me.<br>So I decide to only write SQL from now, no more ORM for me.<br>But if there is any cool ORM for Go, I guess I try.<p>This guide is not kind of guide which cover all cases.<br>Just my little tricks when I work with SQL.<h1>Stay away from database unique id</h1><p>Use UUID instead.<h1>Stay away from database timestamp</h1><p>Stay away from all kind of timestamp, timestamp of MySQL or any database.<br>Just use int64 then pass the timestamp in service layer not database layer.<p>Why? Because time and date and location are too much complex to handle.<br>In my business, I use timestamp in milliseconds.<br>Then I save timestamp as int64 value to database.<br>Each time I get timestamp from database, I parse to time struct in Go with location or format I want.<br>No more hassle!<h1>Use index</h1><p>You should use index for faster query, but not too much.<br>Don't create index for every fields in table.<br>Choose wisely!<p>For example, create index in MySQL:<pre><code class=language-sql>CREATE INDEX `idx_timestamp`
ON `user_upload` (`timestamp`);
</code></pre><h1>Be careful with NULL</h1><p>If compare with field which can be NULL, remember to check NULL for safety.<pre><code class=language-sql>-- field_something can be NULL
-- Don't
SELECT *
FROM table
WHERE field_something != 1
-- Do
SELECT *
FROM table
WHERE (field_something IS NULL OR field_something != 1)
</code></pre><h1>Thanks</h1><ul><li><a href=https://use-the-index-luke.com/>Use The Index, Luke</a><li><a href=https://www.foxhound.systems/blog/essential-elements-of-high-performance-sql-indexes/>Essential elements of high performance applications: SQL indexes</a><li><a href=https://architecturenotes.co/things-you-should-know-about-databases/>Things You Should Know About Databases</a></ul><a href=mailto:hauvipapro+posts@gmail.com>Feel free to ask me via email</a>

22
posts/2022-07-31-sql.md
View File

@ -8,6 +8,10 @@ But if there is any cool ORM for Go, I guess I try.
This guide is not kind of guide which cover all cases.
Just my little tricks when I work with SQL.
# Stay away from database unique id
Use UUID instead.
# Stay away from database timestamp
Stay away from all kind of timestamp, timestamp of MySQL or any database.
@ -32,6 +36,24 @@ CREATE INDEX `idx_timestamp`
ON `user_upload` (`timestamp`);
```
# Be careful with NULL
If compare with field which can be NULL, remember to check NULL for safety.
```sql
-- field_something can be NULL
-- Don't
SELECT *
FROM table
WHERE field_something != 1
-- Do
SELECT *
FROM table
WHERE (field_something IS NULL OR field_something != 1)
```
# Thanks
- [Use The Index, Luke](https://use-the-index-luke.com/)