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Merge pull request #457 from camsaul/add-section-about-order-by-nulls-last

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Add section about `ORDER BY ... NULLS LAST` to 1.x differences dox
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Sean Corfield 2023-02-08 11:14:10 -08:00 committed by GitHub
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doc/differences-from-1-x.md
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@ -189,6 +189,26 @@ user=> (sql/format {:select [[[:exists {:select [:a] :from [:foo]}] :x]]})
["SELECT EXISTS (SELECT a FROM foo) AS x"]
```
### `ORDER BY` with `NULLS FIRST` or `NULLS LAST`
In HoneySQL 1.x, if you wanted to generate SQL like
```sql
ORDER BY ... DESC NULLS LAST
```
you needed to pass `:nulls-last` as a separate keyword, after `:asc` or `:desc`:
```clj
{:order-by [[:my-column :desc :nulls-last]]}
```
In HoneySQL 2.x, the direction and the null ordering rule are now combined into a single keyword:
```clj
{:order-by [[:my-column :desc-nulls-last]]}
```
## Extensibility
The protocols and multimethods in 1.x have all gone away. The primary extension point is `honey.sql/register-clause!` which lets you specify the new clause (keyword), the formatter function for it, and the existing clause that it should be ranked before (`format` processes the DSL in clause order).