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Using SQL

The SQL library helps you build and serialize SQL queries in Swift. It has an extensible, protocol-based design that supports many standard SQL queries like:

  • SELECT, INSERT, UPDATE, DELETE
  • CREATE TABLE, ALTER TABLE, DROP TABLE
  • CREATE INDEX, DROP INDEX

This package also integrates deeply with Codable and parameter binding to make working with your database fast and secure.

This guide assumes you have already chosen and configured a driver in SQL → Getting Started. In some cases, these SQL dialects will have different syntaxes or supported features. Be sure to check their API docs for additional functionality.

Connection

The first step to building a SQL query is getting access to a connection. Most often, you will use withPooledConnection(to:) followed by your database's dbid.

Note

Refer to the table in SQL → Getting Started for your database's default dbid. The dbid allows you to use multiple databases per application.

router.get("sql") { req in
    return req.withPooledConnection(to: .<#dbid#>) { conn in
        return // use conn to perform a query
    }
}

Check out Database Kit → Overview → Connections for more information. The rest of this guide will assume you have access to a SQL database connection.

Select

Use the select() method on a connection to create a SQLSelectBuilder. This builder helps you create SELECT statements and supports:

  • *, columns, and expressions like functions
  • FROM
  • JOIN
  • GROUP BY
  • ORDER BY

The select builder conforms to SQLPredicateBuilder for building WHERE predicates. It also conforms to SQLQueryFetcher for decoding Codable models from the result set.

Let's take a look at an example SELECT query. Replace the Xcode placeholder with the name of the database you are using, i.e., SQLite.

struct User: SQLTable, Codable {
    static let sqlTableIdentifierString = "users"
    let id: Int?
    let name: String
}

let users = conn.select()
    .all().from(User.self)
    .where(\User.name == "Vapor")
    .all(decoding: User.self)
print(users) // Future<[User]>

The resulting SQL will look something like this:

SELECT * FROM "users" WHERE "users"."name" = ?

As you can see, the Swift code reads similarly to actual SQL. Be sure to visit the API docs for the various builder protocols to see all available methods.

API Docs

Check out the API docs for more in-depth information about SQL's APIs.

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