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https://github.com/crystal-lang/crystal-db

Common db api for crystal
https://github.com/crystal-lang/crystal-db

crystal database

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Common db api for crystal

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# crystal-db



Common db api for crystal. You will need to have a specific driver to access a database.



* [SQLite](https://github.com/crystal-lang/crystal-sqlite3)

* [MySQL](https://github.com/crystal-lang/crystal-mysql)

* [PostgreSQL](https://github.com/will/crystal-pg)

* [ODBC](https://github.com/naqvis/crystal-odbc)

* [Cassandra](https://github.com/kaukas/crystal-cassandra)

* [DuckDB](https://github.com/amauryt/crystal-duckdb)

* [Microsoft SQL Server](https://github.com/wonderix/crystal-tds)



## Installation



If you are creating a shard that will work with _any_ driver, then add `crystal-db` as a dependency in `shard.yml`:



```yaml

dependencies:

  db:

    github: crystal-lang/crystal-db

```



If you are creating an application that will work with _some specific_ driver(s), then add them in `shard.yml`:



```yaml

dependencies:

  sqlite3:

    github: crystal-lang/crystal-sqlite3

```



`crystal-db` itself will be a nested dependency if drivers are included.



Note: Multiple drivers can be included in the same application.



## Documentation



* [Latest API](https://crystal-lang.github.io/crystal-db/api/latest/)

* [Crystal book](https://crystal-lang.org/docs/database/)



## Usage



This shard only provides an abstract database API. In order to use it, a specific driver for the intended database has to be required as well:



The following example uses SQLite where `?` indicates the arguments. If PostgreSQL is used `$1`, `$2`, etc. should be used. `crystal-db` does not interpret the statements.



```crystal

require "db"

require "sqlite3"



DB.open "sqlite3:./file.db" do |db|

  # When using the pg driver, use $1, $2, etc. instead of ?

  db.exec "create table contacts (name text, age integer)"

  db.exec "insert into contacts values (?, ?)", "John Doe", 30



  args = [] of DB::Any

  args << "Sarah"

  args << 33

  db.exec "insert into contacts values (?, ?)", args: args



  puts "max age:"

  puts db.scalar "select max(age) from contacts" # => 33



  puts "contacts:"

  db.query "select name, age from contacts order by age desc" do |rs|

    puts "#{rs.column_name(0)} (#{rs.column_name(1)})"

    # => name (age)

    rs.each do

      puts "#{rs.read(String)} (#{rs.read(Int32)})"

      # => Sarah (33)

      # => John Doe (30)

    end

  end

end

```



## Roadmap



Issues not yet addressed:



- [x] Support non prepared statements. [#25](https://github.com/crystal-lang/crystal-db/pull/25)

- [x] Time data type. (implementation details depends on actual drivers)

- [x] Data type extensibility. Allow each driver to extend the data types allowed.

- [x] Transactions & nested transactions. [#27](https://github.com/crystal-lang/crystal-db/pull/27)

- [x] Connection pool.

- [x] Logging

- [ ] Direct access to `IO` to avoid memory allocation for blobs.



## Contributing



1. Fork it ( https://github.com/crystal-lang/crystal-db/fork )

2. Create your feature branch (git checkout -b my-new-feature)

3. Commit your changes (git commit -am 'Add some feature')

4. Push to the branch (git push origin my-new-feature)

5. Create a new Pull Request



## Contributors



- [bcardiff](https://github.com/bcardiff) Brian J. Cardiff - creator, maintainer