82 lines
1.9 KiB
Markdown
82 lines
1.9 KiB
Markdown
---
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categories:
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- Databases
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- Programming Languages
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tags: [SQL]
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---
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# SQL: The SELECT query
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## Print/retrieve/write an entire table, unfiltered
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```sql
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SELECT * FROM [table_name]
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SELECT * FROM model
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```
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## Retrieve all data from a specific field
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```sql
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SELECT [field_name] FROM [table_name]
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SELECT name FROM manufacturer
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```
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## Retrieve data and order it
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This example orders alphabetically:
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```sql
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SELECT [field_name] FROM [table_name] ORDER BY [property]
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SELECT name FROM model ORDER BY name
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```
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> When `ORDER BY` is used the default method for strings is alphabetical and for integers it is ascending order.
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Here's a more complex real-life request:
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```sql
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SELECT name, cores, ram FROM model ORDER BY ram, name
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```
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It gives us:
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```
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name cores ram
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---------------- ---------- ----------
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Commodore VIC-20 1 0.005
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Commodore 64 1 0.064
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Amiga 500 1 0.5
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Apple Lisa 1 1.0
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Raspberry Pi 1 M 1 256.0
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Raspberry Pi 1 M 1 256.0
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Raspberry Pi 1 M 1 512.0
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Raspberry Pi 1 M 1 512.0
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Raspberry Pi 1 M 1 512.0
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Raspberry Pi Zer 1 512.0
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```
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But we can obviously specify our own ordering method:
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```sql
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SELECT name, cores, release_date FROM model ORDER BY cores DESC, name;
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```
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Returns:
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```
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name cores release_date
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----------------- ---------- ------------
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Apple MacBook Pro 6 2019-05-21
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Apple iMac 4 2019-03-19
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Raspberry Pi 2 Mo 4 2015-02-01
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Raspberry Pi 3 Mo 4 2018-11-01
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Raspberry Pi 3 Mo 4 2016-02-01
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Raspberry Pi 3 Mo 4 2018-03-14
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Raspberry Pi 4 Mo 4 2019-06-24
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Raspberry Pi 4 Mo 4 2019-06-24
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Raspberry Pi 4 Mo 4 2019-06-24
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```
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> `ORDER BY` always comes last, after the selection and any filtering clauses but _before_ a `WHERE` clause
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