2023-03-24 03:49:34 +00:00
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# Other Databases
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There is a dedicated section for [PostgreSQL Support](postgres.md).
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This section provides hints and tips for generating SQL for other
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databases.
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As a reminder, HoneySQL supports the following dialects out of the box:
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* `:ansi` -- which is the default and provides broad support for PostgreSQL as well
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* `:mysql` -- which includes MariaDB and Percona
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2023-10-28 21:04:35 +00:00
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* `:nrql` -- as of 2.5.1090
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2023-03-24 03:49:34 +00:00
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* `:oracle`
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* `:sqlserver` -- Microsoft SQL Server
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For the most part, these dialects only change the "stropping" --
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how SQL entities are quoted in the generated SQL -- but dialects
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can change clause order and/or add dialect-specific clauses.
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This section is a work-in-progress and more hints and tips will be
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added over time for more databases.
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## Precedence
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The biggest difference between database dialects tends to be
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precedence. MySQL actually has different precedence in the `SET`
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clause but several databases disagree on the precedence of actual
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"set" operations: `UNION`, `EXCEPT`, `INTERSECT`, etc.
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HoneySQL tries to be fairly neutral in this area and follows ANSI SQL
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precedence. This means that some databases may have problems with
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complex SQL operations that combine multiple clauses with contentious
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precedence. In general, you can solve this using the `:nest`
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pseudo-clause in the DSL:
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<!-- :test-doc-blocks/skip -->
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```clojure
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{:nest DSL}
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;; will produce DSL wrapped in ( .. )
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```
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This should allow you to cater to various databases' precedence
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peculiarities.
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## BigQuery (Google)
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Function names can be case-sensitive: you can use the "as-is" notation
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for SQL entities to avoid conversion to upper-case: `[:'domain :ref]`
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produces `domain(ref)` rather than `DOMAIN(ref)`.
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## ClickHouse
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This is another case-sensitive database than requires the "as-is"
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notation described for **BigQuery** above.
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`WITH expr AS ident` is supported as a core part of the DSL,
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as of 2.4.962.
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## MySQL
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When you select the `:mysql` dialect, the precedence of `:set` is
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changed. All the other databases get this correct.
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`REPLACE INTO`, while specific to MySQL and SQLite, is supported as
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a core part of the DSL, as `:replace-into`, as of 2.4.969.
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## SQLite
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Precedence of "set" operations: SQLite differs from other databases
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in handling compound SQL operations that use multiple `UNION`,
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`EXCEPT`, `INTERSECT` clauses. Use `:nest` to disambiguate your
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intentions.
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See issue [#462](https://github.com/seancorfield/honeysql/issues/462)
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for some background on this.
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`INSERT OR IGNORE INTO`: this syntax is specific to SQLite for
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performing upserts. However, SQLite supports the PostgreSQL-style
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upsert with `ON CONFLICT` so you can use that syntax instead, for
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`DO NOTHING` and `DO UPDATE SET`. In addition,
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`INSERT OR REPLACE INTO` can be written using just `REPLACE INTO`
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(see below).
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Issue [#448](https://github.com/seancorfield/honeysql/issues/448)
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has more background on this.
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`REPLACE INTO`, while specific to MySQL and SQLite, is supported as
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a core part of the DSL, as `:replace-into`, as of 2.4.969.
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