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SQLite.swift Documentation

Installation

Note: SQLite.swift requires Swift 1.1 (and Xcode 6.1) or greater.

To install SQLite.swift as an Xcode sub-project:

  1. Drag the SQLite.xcodeproj file into your own project. (Submodule, clone, or download the project first.)

    Installation

  2. In your target’s Build Phases, add SQLite iOS (or SQLite Mac) to the Target Dependencies build phase.

  3. Add the appropriate SQLite.framework product to the Link Binary With Libraries build phase.

  4. Add the same SQLite.framework to a Copy Files build phase with a Frameworks destination. (Add a new build phase if need be.)

You should now be able to import SQLite from any of your target’s source files and begin using SQLite.swift.

Getting Started

To use SQLite.swift classes or structures in your target’s source file, first import the SQLite module.

import SQLite

Connecting to a Database

Database connections are established using the Database class. A database is initialized with a path. SQLite will attempt to create the database file if it does not already exist.

let db = Database("path/to/db.sqlite3")

Read-Write Databases

On iOS, you can create a writable database in your app’s Documents directory.

let path = NSSearchPathForDirectoriesInDomains(
    .DocumentDirectory, .UserDomainMask, true
).first as String

let db = Database("\(path)/db.sqlite3")

On OS X, you can use your app’s Application Support directory:

var path = NSSearchPathForDirectoriesInDomains(
    .ApplicationSupportDirectory, .UserDomainMask, true
).first as String + NSBundle.mainBundle().bundleIdentifier!

// create parent directory iff it doesn't exist
NSFileManager.defaultManager().createDirectoryAtPath(
    path, withIntermediateDirectories: true, attributes: nil, error: nil
)

let db = Database("\(path)/db.sqlite3")

Read-Only Databases

If you bundle a database with your app, you can establish a read-only connection to it.

let path = NSBundle.mainBundle().pathForResource("db", ofType: "sqlite3")!

let db = Database(path, readonly: true)

Note: Signed applications cannot modify their bundle resources. If you bundle a database file with your app for the purpose of bootstrapping, copy it to a writable location before establishing a connection (see Read-Write Databases, above, for typical, writable locations).

In-Memory Databases

If you omit the path, SQLite.swift will provision an in-memory database.

let db = Database() // equivalent to `Database(":memory:")`

To create a temporary, disk-backed database, pass an empty file name.

let db = Database("")

In-memory databases are automatically deleted when the database connection is closed.

A Note on Thread-Safety

Note: Every database comes equipped with its own serial queue for statement execution and can be safely accessed across threads. Threads that open transactions and savepoints, however, do not block other threads from executing statements within the transaction.

Building Type-Safe SQL

SQLite.swift comes with a typed expression layer that directly maps Swift types to their SQLite counterparts.

Swift Type SQLite Type
Int INTEGER
Double REAL
String TEXT
Bool BOOLEAN
nil NULL
SQLite.Blob* BLOB

*SQLite.swift defines its own Blob structure, which safely wraps the underlying bytes.

See Custom Types for more information about extending other classes and structures to work with SQLite.swift.

These expressions (in the form of the structure, Expression) build on one another and, with a query (Query), can create and execute SQL statements.

Expressions

Expressions are generic structures associated with a type (built-in or custom), raw SQL, and (optionally) values to bind to that SQL. Typically, you will only explicitly create expressions to describe your columns, and typically only once per column.

let id = Expression<Int>("id")
let email = Expression<String>("email")
let balance = Expression<Double>("balance")
let verified = Expression<Bool>("verified")

Use optional generics for expressions that can evaluate to NULL.

let name = Expression<String?>("name")

Note: The default Expression initializer is for quoted identifiers (i.e., column names). To build a literal SQL expression, use init(literal:).

Compound Expressions

Expressions can be combined with other expressions and types using filters, and other operators and functions. These building blocks can create complex SQLite statements.

Queries

Queries are structures that reference a database and table name, and can be used to build a variety of statements using expressions. We can create a Query by subscripting a database connection with a table name.

let users = db["users"]

Assuming the table exists, we can immediately insert, select, update, and delete rows.

Creating a Table

We can run CREATE TABLE statements by calling the create(table:) function on a database connection. The following is a basic example of SQLite.swift code (using the expressions and query above) and the corresponding SQL it generates.

db.create(table: users) { t in     // CREATE TABLE "users" (
    t.column(id, primaryKey: true) //     "id" INTEGER PRIMARY KEY NOT NULL,
    t.column(email, unique: true)  //     "email" TEXT UNIQUE NOT NULL,
    t.column(name)                 //     "name" TEXT
}                                  // )

Note: Expression<T> structures (in this case, the id and email columns), generate NOT NULL constraints automatically, while Expression<T?> structures (name) do not.

Create Table Options

The create(table:) function has several default parameters we can override.

  • temporary adds a TEMPORARY clause to the CREATE TABLE statement (to create a temporary table that will automatically drop when the database connection closes). Default: false.

    db.create(table: users, temporary: true) { t in /* ... */ }
// CREATE TEMPORARY TABLE "users" -- ...

  • ifNotExists adds an IF NOT EXISTS clause to the CREATE TABLE statement (which will bail out gracefully if the table already exists). Default: false.

    db.create(table: users, ifNotExists: true) { t in /* ... */ }
// CREATE TABLE "users" IF NOT EXISTS -- ...

Column Constraints

The column function is used for a single column definition. It takes an expression describing the column name and type, and accepts several parameters that map to various column constraints and clauses.

  • primaryKey adds an INTEGER PRIMARY KEY constraint to a single column. (See the primaryKey function under Table Constraints for non-integer primary keys).

    t.column(id, primaryKey: true)
// "id" INTEGER PRIMARY KEY NOT NULL

    Note: The primaryKey parameter cannot be used alongside defaultValue or references. If you need to create a column that has a default value and is also a primary and/or foreign key, use the primaryKey and foreignKey functions mentioned under Table Constraints.

    Primary keys cannot be optional (Expression<Int?>).

  • unique adds a UNIQUE constraint to the column. (See the unique function under Table Constraints for uniqueness over multiple columns).

    t.column(email, unique: true)
// "email" TEXT UNIQUE NOT NULL

  • check attaches a CHECK constraint to a column definition in the form of a boolean expression (Expression<Bool>). Boolean expressions can be easily built using filter operators and functions. (See also the check function under Table Constraints.)

    t.column(email, check: like("%@%", email))
// "email" TEXT NOT NULL CHECK ("email" LIKE '%@%')

  • defaultValue adds a DEFAULT clause to a column definition and only accepts a value (or expression) matching the column’s type. This value is used if none is explicitly provided during an INSERT.

    t.column(name, defaultValue: "Anonymous")
// "name" TEXT DEFAULT 'Anonymous'

    Note: The defaultValue parameter cannot be used alongside primaryKey and references. If you need to create a column that has a default value and is also a primary and/or foreign key, use the primaryKey and foreignKey functions mentioned under Table Constraints.

  • collate adds a COLLATE clause to Expression<String> (and Expression<String?>) column definitions with a collating sequence defined in the Collation enumeration.

    t.column(email, collate: .NoCase)
// "email" TEXT NOT NULL COLLATE NOCASE

  • references adds a REFERENCES clause to Expression<Int> (and Expression<Int?>) column definitions and accepts a table (Query) or namespaced column expression. (See the foreignKey function under Table Constraints for non-integer foreign key support.)

    t.column(user_id, references: users[id])
// "user_id" INTEGER REFERENCES "users"("id")

t.column(user_id, references: users)
// "user_id" INTEGER REFERENCES "users"
// -- assumes "users" has a PRIMARY KEY

    Note: The references parameter cannot be used alongside primaryKey and defaultValue. If you need to create a column that has a default value and is also a primary and/or foreign key, use the primaryKey and foreignKey functions mentioned under Table Constraints.

Table Constraints

Additional constraints may be provided outside the scope of a single column using the following functions.

  • primaryKey adds a PRIMARY KEY constraint to the table. Unlike the column constraint, above, it supports all SQLite types, ascending and descending orders, and composite (multiple column) keys.

    t.primaryKey(email.asc, name)
// PRIMARY KEY("email" ASC, "name")

  • unique adds a UNIQUE constraint to the table. Unlike the column constraint, above, it supports composite (multiple column) constraints.

    t.unique(local, domain)
// UNIQUE("local", "domain")

  • check adds a CHECK constraint to the table in the form of a boolean expression (Expression<Bool>). Boolean expressions can be easily built using filter operators and functions. (See also the check parameter under Column Constraints.)

    t.check(balance >= 0)
// CHECK ("balance" >= 0.0)

  • foreignKey adds a FOREIGN KEY constraint to the table. Unlike the references constraint, above, it supports all SQLite types, and both ON UPDATE and ON DELETE actions.

    t.foreignKey(user_id, on: users[id], delete: .SetNull)
// FOREIGN KEY("user_id") REFERENCES "users"("id") ON DELETE SET NULL

    Note: Composite foreign keys are not supported at this time. If you add support, please submit a pull request.

Inserting Rows

We can insert rows into a table by calling a query’s insert function with a list of setters, typically typed column expressions and values (which can also be expressions), each joined by the <- operator.

users.insert(email <- "alice@mac.com", name <- "Alice")?
// INSERT INTO "users" ("email", "name") VALUES ('alice@mac.com', 'Alice')

The insert function can return several different types that are useful in different contexts.

  • An Int? representing the inserted row’s ROWID (or nil on failure), for simplicity.

    if let insertID = users.insert(email <- "alice@mac.com") {
    println("inserted id: \(insertID)")
}

    We can use the optional nature of the value to disambiguate with a simple ? or !.

    // ignore failure
users.insert(email <- "alice@mac.com")?

// assertion on failure
users.insert(email <- "alice@mac.com")!

  • A Statement, for the transaction and savepoint helpers that take a list of statements.

    db.transaction(
    users.insert(email <- "alice@mac.com"),
    users.insert(email <- "betty@mac.com")
)
// BEGIN DEFERRED TRANSACTION;
// INSERT INTO "users" ("email") VALUES ('alice@mac.com');
// INSERT INTO "users" ("email") VALUES ('betty@mac.com');
// COMMIT TRANSACTION;

  • A tuple of the above ROWID and statement: (ID: Int?, Statement), for flexibility.

    let (ID, statement) = users.insert(email <- "alice@mac.com")
if let ID = ID {
    println("inserted id: \(ID)")
} else if statement.failed {
    println("insertion failed: \(statement.reason)")
}

The update and delete functions follow similar patterns.

Note: If insert is called without any arguments, the statement will run with a DEFAULT VALUES clause. The table must not have any constraints that aren’t fulfilled by default values.

timestamps.insert()!
// INSERT INTO "timestamps" DEFAULT VALUES

Setters

SQLite.swift typically uses the <- operator to set values during inserts and updates.

views.update(count <- 0)
// UPDATE "views" SET "count" = 0 WHERE ("id" = 1)

There are also a number of convenience setters that take the existing value into account using native Swift operators.

For example, to atomically increment a column, we can use ++:

views.update(count++) // equivalent to `views.update(count -> count + 1)`
// UPDATE "views" SET "count" = "count" + 1 WHERE ("id" = 1)

To take an amount and “move” it via transaction, we can use -= and +=:

let amount = 100.0
db.transaction(
    alice.update(balance -= amount),
    betty.update(balance += amount)
)
// BEGIN DEFERRED TRANSACTION;
// UPDATE "users" SET "balance" = "balance" - 100.0 WHERE ("id" = 1);
// UPDATE "users" SET "balance" = "balance" + 100.0 WHERE ("id" = 2);
// COMMIT TRANSACTION;
Infix Setters
Operator Types
<- Value -> Value
+= Number -> Number
-= Number -> Number
*= Number -> Number
/= Number -> Number
%= Int -> Int
<<= Int -> Int
>>= Int -> Int
&= Int -> Int
`
^= Int -> Int
+= String -> String
Postfix Setters
Operator Types
++ Int -> Int
-- Int -> Int

Selecting Rows

Query structures are SELECT statements waiting to happen. They execute via iteration and other means of sequence access.

Iterating and Accessing Values

Queries execute lazily upon iteration. Each row is returned as a Row object, which can be subscripted with a column expression matching one of the columns returned.

for user in users {
    println("id: \(user[id]), email: \(user[email]), name: \(user[name])")
    // id: 1, email: alice@mac.com, name: Optional("Alice")
}
// SELECT * FROM "users"

Expression<T> column values are automatically unwrapped (we’ve made a promise to the compiler that they’ll never be NULL), while Expression<T?> values remain wrapped.

Plucking Rows

We can pluck the first row by calling the first computed property on Query.

if let user = users.first { /* ... */ } // Row
// SELECT * FROM "users" LIMIT 1

To collect all rows into an array, we can simply wrap the sequence (though this is not always the most memory-efficient idea).

let all = Array(users)
// SELECT * FROM "users"

Building Complex Queries

Query structures have a number of chainable functions that can be used (with expressions) to add and modify a number of clauses to the underlying statement.

let query = users.select(email)           // SELECT "email" FROM "users"
                 .filter(name != nil)     // WHERE "name" IS NOT NULL
                 .order(email.desc, name) // ORDER BY "email" DESC, "name"
                 .limit(5, offset: 1)     // LIMIT 5 OFFSET 1

Selecting Columns

By default, Query objects select every column of the result set (using SELECT *). We can use the select function with a list of expressions to return specific columns instead.

let query = users.select(id, email)
// SELECT "id", "email" FROM "users"

Joining Other Tables

We can join tables using a query’s join function.

users.join(posts, on: user_id == users[id])
// SELECT * FROM "users" INNER JOIN "posts" ON ("user_id" = "users"."id")

The join function takes a query object (for the table being joined on), a join condition (on), and is prefixed with an optional join type (default: .Inner). Join conditions can be built using filter operators and functions, generally require namespacing, and sometimes require aliasing.

Column Namespacing

When joining tables, column names can become ambiguous. E.g., both tables may have an id column.

let query = users.join(posts, on: user_id == id)
// assertion failure: ambiguous column 'id'

We can disambiguate by namespacing id.

let query = users.join(posts, on: user_id == users[id])
// SELECT * FROM "users" INNER JOIN "posts" ON ("user_id" = "users"."id")

Namespacing is achieved by subscripting a query with a column expression (e.g., users[id] above becomes users.id).

Note: We can namespace all of a table’s columns using *.

let query = users.select(users[*])
// SELECT "users".* FROM "users"
Table Aliasing

Occasionally, we need to join a table to itself, in which case we must alias the table with another name. We can achieve this using the query’s alias function.

let managers = users.alias("managers")

let query = users.join(managers, on: managers[id] == users[manager_id])
// SELECT * FROM "users"
// INNER JOIN "users" AS "managers" ON ("managers"."id" = "users"."manager_id")

If query results can have ambiguous column names, row values should be accessed with namespaced column expressions. In the above case, SELECT * immediately namespaces all columns of the result set.

let user = query.first!
user[id]           // fatal error: ambiguous column 'id'
                   // (please disambiguate: ["users"."id", "managers"."id"])

user[users[id]]    // returns "users"."id"
user[managers[id]] // returns "managers"."id"

Filtering Rows

SQLite.swift filters rows using a query’s filter function with a boolean expression (Expression<Bool>).

users.filter(id == 1)
// SELECT * FROM "users" WHERE ("id" = 1)

users.filter(contains([1, 2, 3, 4, 5], id))
// SELECT * FROM "users" WHERE ("id" IN (1, 2, 3, 4, 5))

users.filter(like("%@mac.com", email))
// SELECT * FROM "users" WHERE ("email" LIKE '%@mac.com')

users.filter(verified && lower(name) == "alice")
// SELECT * FROM "users" WHERE ("verified" AND (lower("name") == 'alice'))

users.filter(verified || balance >= 10_000)
// SELECT * FROM "users" WHERE ("verified" OR ("balance" >= 10000.0))

You can build your own boolean expressions by using one of the many filter operators and functions.

Note: SQLite.swift defines filter instead of where because where is a reserved keyword.

Filter Operators and Functions

SQLite.swift defines a number of operators for building filtering predicates. Operators and functions work together in a type-safe manner, so attempting to equate or compare different types will prevent compilation.

Infix Filter Operators
Swift Types SQLite
== Equatable -> Bool =/IS*
!= Equatable -> Bool !=/IS NOT*
> Comparable -> Bool >
>= Comparable -> Bool >=
< Comparable -> Bool <
<= Comparable -> Bool <=
~= (Interval, Comparable) -> Bool BETWEEN
&& Bool -> Bool AND
` `

*When comparing against nil, SQLite.swift will use IS and IS NOT accordingly.

Prefix Filter Operators
Swift Types SQLite
! Bool -> Bool NOT
Filtering Functions
Swift Types SQLite
like String -> Bool LIKE
glob String -> Bool GLOB
match String -> Bool MATCH
contains (Array<T>, T) -> Bool IN

Sorting Rows

We can pre-sort returned rows using the query’s order function.

E.g., to return users sorted by email, then name, in ascending order:

users.order(email, name)
// SELECT * FROM "users" ORDER BY "email", "name"

The order function takes a list of column expressions.

Expression objects have two computed properties to assist sorting: asc and desc. These properties append the expression with ASC and DESC to mark ascending and descending order respectively.

users.order(email.desc, name.asc)
// SELECT * FROM "users" ORDER BY "email" DESC, "name" ASC

Limiting and Paging Results

We can limit and skip returned rows using a query’s limit function (and its optional offset parameter).

users.limit(5)
// SELECT * FROM "users" LIMIT 5

users.limit(5, offset: 5)
// SELECT * FROM "users" LIMIT 5 OFFSET 5

Aggregation

Query structures come with a number of functions that quickly return aggregate values from the table. These mirror the core aggregate functions and are executed immediately against the query.

users.count
// SELECT count(*) FROM "users"

Filtered queries will appropriately filter aggregate values.

users.filter(name != nil).count
// SELECT count(*) FROM "users" WHERE "name" IS NOT NULL

  • count as a computed property (see examples above) returns the total number of rows matching the query.

    count as a function takes a column name and returns the total number of rows where that column is not NULL.

    users.count(name) // -> Int
// SELECT count("name") FROM "users"

  • max takes a comparable column expression and returns the largest value if any exists.

    users.max(id) // -> Int?
// SELECT max("id") FROM "users"

  • min takes a comparable column expression and returns the smallest value if any exists.

    users.min(id) // -> Int?
// SELECT min("id") FROM "users"

  • average takes a numeric column expression and returns the average row value (as a Double) if any exists.

    users.average(balance) // -> Double?
// SELECT avg("balance") FROM "users"

  • sum takes a numeric column expression and returns the sum total of all rows if any exist.

    users.sum(balance) // -> Double?
// SELECT sum("balance") FROM "users"

  • total, like sum, takes a numeric column expression and returns the sum total of all rows, but in this case always returns a Double, and returns 0.0 for an empty query.

    users.total(balance) // -> Double
// SELECT total("balance") FROM "users"

Note: Most of the above aggregate functions (except max and min) can be called with a distinct parameter to aggregate DISTINCT values only.

users.count(distinct: name)
// SELECT count(DISTINCT "name") FROM "users"

Updating Rows

We can update a table’s rows by calling a query’s update function with a list of setters, typically typed column expressions and values (which can also be expressions), each joined by the <- operator.

When an unscoped query calls update, it will update every row in the table.

users.update(email <- "alice@me.com")?
// UPDATE "users" SET "email" = 'alice@me.com'

Be sure to scope UPDATE statements beforehand using the filter function.

let alice = users.filter(id == 1)
alice.update(email <- "alice@me.com")?
// UPDATE "users" SET "email" = 'alice@me.com' WHERE ("id" = 1)

Like insert (and delete), update can return several different types that are useful in different contexts.

  • An Int? representing the number of updated rows (or nil on failure), for simplicity.

    if alice.update(email <- "alice@me.com") > 0 {
    println("updated Alice")
}

    We can use the optional nature of the value to disambiguate with a simple ? or !.

    // ignore failure
alice.update(email <- "alice@me.com")?

// assertion on failure
alice.update(email <- "alice@me.com")!

  • A Statement, for the transaction and savepoint helpers that take a list of statements.

  • A tuple of the above number of updated rows and statement: (changes: Int?, Statement), for flexibility.

Deleting Rows

We can delete rows from a table by calling a query’s delete function.

When an unscoped query calls delete, it will delete every row in the table.

users.delete()?
// DELETE FROM "users"

Be sure to scope DELETE statements beforehand using the filter function.

let alice = users.filter(id == 1)
alice.delete()?
// DELETE FROM "users" WHERE ("id" = 1)

Like insert and update, delete can return several different types that are useful in different contexts.

  • An Int? representing the number of deleted rows (or nil on failure), for simplicity.

    if alice.delete() > 0 {
    println("deleted Alice")
}

    We can use the optional nature of the value to disambiguate with a simple ? or !.

    // ignore failure
alice.delete()?

// assertion on failure
alice.delete()!

  • A Statement, for the transaction and savepoint helpers that take a list of statements.

  • A tuple of the above number of deleted rows and statement: (changes: Int?, Statement), for flexibility.

Transactions and Savepoints

Using the transaction and savepoint functions, we can run a series of statements, commiting the changes to the database if they all succeed. If a single statement fails, we bail out early and roll back.

db.transaction(
    users.insert(email <- "betty@icloud.com"),
    users.insert(email <- "cathy@icloud.com", manager_id <- db.lastID)
)

Note: Each statement is captured in an auto-closure and won’t execute till the preceding statement succeeds. This means we can use the lastID property on Database to reference the previous statement’s insert ROWID.

Altering the Schema

SQLite.swift comes with several functions (in addition to create(table:)) for altering a database schema in a type-safe manner.

Renaming Tables

We can rename a table by calling the rename(table:to:) function on a database connection.

db.rename(users, to: "users_old")
// ALTER TABLE "users" RENAME TO "users_old"

Adding Columns

We can add columns to a table by calling alter function on a database connection. SQLite.swift enforces the same limited subset of ALTER TABLE that SQLite supports.

db.alter(table: users, add: suffix)
// ALTER TABLE "users" ADD COLUMN "suffix" TEXT

Added Column Constraints

The alter function shares several of the same column function parameters used when creating tables.

  • check attaches a CHECK constraint to a column definition in the form of a boolean expression (Expression<Bool>). (See also the check function under Table Constraints.)

    let check = contains(["JR", "SR"], suffix)
db.alter(table: users, add: suffix, check: check)
// ALTER TABLE "users"
// ADD COLUMN "suffix" TEXT CHECK ("suffix" IN ('JR', 'SR'))

  • defaultValue adds a DEFAULT clause to a column definition and only accepts a value matching the column’s type. This value is used if none is explicitly provided during an INSERT.

    db.alter(table: users, add: suffix, defaultValue: "SR")
// ALTER TABLE "users" ADD COLUMN "suffix" TEXT DEFAULT 'SR'

    Note: Unlike the CREATE TABLE constraint, default values may not be expression structures (including CURRENT_TIME, CURRENT_DATE, or CURRENT_TIMESTAMP).

  • references adds a REFERENCES clause to Int (and Int?) column definitions and accepts a table or namespaced column expression. (See the foreignKey function under Table Constraints for non-integer foreign key support.)

    db.alter(table: posts, add: user_id, references: users[id])
// ALTER TABLE "posts" ADD COLUMN "user_id" INTEGER REFERENCES "users"("id")

db.alter(table: posts, add: user_id, references: users)
// ALTER TABLE "posts" ADD COLUMN "user_id" INTEGER REFERENCES "users"
// -- assumes "users" has a PRIMARY KEY

Indexes

Creating Indexes

We can run CREATE INDEX statements by calling the create(index:) function on a database connection.

db.create(index: users, on: email)
// CREATE INDEX "index_users_on_email" ON "users" ("email")

The index name is generated automatically based on the table and column names.

The create(index:) function has a couple default parameters we can override.

  • unique adds a UNIQUE constraint to the index. Default: false.

    db.create(index: users, on: email, unique: true)
// CREATE UNIQUE INDEX "index_users_on_email" ON "users" ("email")

  • ifNotExists adds an IF NOT EXISTS clause to the CREATE TABLE statement (which will bail out gracefully if the table already exists). Default: false.

    db.create(index: users, on: email, ifNotExists: true)
// CREATE INDEX IF NOT EXISTS "index_users_on_email" ON "users" ("email")

Dropping Indexes

We can run DROP INDEX statements by calling the drop(index:) function on a database connection.

db.drop(index: users, on: email)
// DROP INDEX "index_users_on_email"

The drop(index:) function has one additional parameter, ifExists, which (when true) adds an IF EXISTS clause to the statement.

db.drop(index: users, on: email, ifExists: true)
// DROP INDEX IF EXISTS "index_users_on_email"

Dropping Tables

We can run DROP TABLE statements by calling the drop(table:) function on a database connection.

db.drop(table: users)
// DROP TABLE "users"

The drop(table:) function has one additional parameter, ifExists, which (when true) adds an IF EXISTS clause to the statement.

db.drop(table: users, ifExists: true)
// DROP TABLE IF EXISTS "users"

Migrations and Schema Versioning

SQLite.swift provides a convenience property on Database to query and set the PRAGMA user_version. This is a great way to manage your schema’s version over migrations.

if db.userVersion == 0 {
    // handle first migration
    db.userVersion = 1
}
if db.userVersion == 1 {
    // handle second migration
    db.userVersion = 2
}

Custom Types

SQLite.swift supports serializing and deserializing any custom type as long as it conforms to the Value protocol.

protocol Value {
    typealias Datatype: Binding
    class var declaredDatatype: String { get }
    class func fromDatatypeValue(datatypeValue: Datatype) -> Self
    var datatypeValue: Datatype { get }
}

The Datatype must be one of the basic Swift types that values are bridged through before serialization and deserialization (see Building Type-Safe SQL for a list of types).

Note: Binding is a protocol that SQLite.swift uses internally to directly map SQLite types to Swift types. Do not conform custom types to the Binding protocol.

Once extended, the type can be used almost wherever typed expressions can be.

Date-Time Values

In SQLite, DATETIME columns can be treated as strings or numbers, so we can transparently bridge NSDate objects through Swift’s String or Int types.

To serialize NSDate objects as TEXT values (in ISO 8601), we’ll use String.

extension NSDate: Value {
    class var declaredDatatype: String {
        return String.declaredDatatype
    }
    class func fromDatatypeValue(stringValue: String) -> NSDate {
        return SQLDateFormatter.dateFromString(stringValue)!
    }
    var datatypeValue: String {
        return SQLDateFormatter.stringFromDate(self)
    }
}

let SQLDateFormatter: NSDateFormatter = {
    let formatter = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
    formatter.timeZone = NSTimeZone(abbreviation: "UTC")
    return formatter
}()

We can also treat them as INTEGER values using Int.

extension NSDate: Value {
    class var declaredDatatype: String {
        return Int.declaredDatatype
    }
    class func fromDatatypeValue(intValue: Int) -> Self {
        return self(timeIntervalSince1970: NSTimeInterval(intValue))
    }
    var datatypeValue: Int {
        return Int(timeIntervalSince1970)
    }
}

Note: SQLite’s CURRENT_DATE, CURRENT_TIME, and CURRENT_TIMESTAMP helpers return TEXT values. Because of this (and the fact that Unix time is far less human-readable when we’re faced with the raw data), we recommend using the TEXT extension.

Once defined, we can use these types directly in SQLite statements.

let published_at = Expression<NSDate>("published_at")

let published = posts.filter(published_at <= NSDate())
// extension where Datatype == String:
//     SELECT * FROM "posts" WHERE "published_at" <= '2014-11-18 12:45:30'
// extension where Datatype == Int:
//     SELECT * FROM "posts" WHERE "published_at" <= 1416314730

Binary Data

Any object that can be encoded and decoded can be stored as a blob of data in SQL.

We can create an NSData bridge rather trivially.

extension NSData: Value {
    class var declaredDatatype: String {
        return Blob.declaredDatatype
    }
    class func fromDatatypeValue(blobValue: Blob) -> Self {
        return self(bytes: blobValue.bytes, length: blobValue.length)
    }
    var datatypeValue: Blob {
        return Blob(bytes: bytes, length: length)
    }
}

We can bridge any type that can be initialized from and encoded to NSData.

// assumes NSData conformance, above
extension UIImage: Value {
    class var declaredDatatype: String {
        return NSData.declaredDatatype
    }
    class func fromDatatypeValue(blobValue: Blob) -> Self {
        return self(data: NSData.fromDatatypeValue(blobValue))
    }
    var datatypeValue: Blob {
        return UIImagePNGRepresentation(self).datatypeValue
    }
}

Note: See the Archives and Serializations Programming Guide for more information on encoding and decoding custom types.

Custom Type Caveats

Swift does not currently support generic subscripting, which means we cannot, by default, subscript Expressions with custom types to:

  1. Namespace expressions. Use the namespace function, instead:

    let avatar = Expression<UIImage?>("avatar")
users[avatar]           // fails to compile
users.namespace(avatar) // "users"."avatar"

  2. Access column data. Use the get function, instead:

    let user = users.first!
user[avatar]            // fails to compile
user.get(avatar)        // UIImage?

We can, of course, write extensions, but they’re rather wordy.

extension Query {
    subscript(column: Expression<UIImage>) -> Expression<UIImage> {
        return namespace(column)
    }
    subscript(column: Expression<UIImage?>) -> Expression<UIImage?> {
        return namespace(column)
    }
}

extension Row {
    subscript(column: Expression<UIImage>) -> UIImage {
        return get(column)
    }
    subscript(column: Expression<UIImage?>) -> UIImage? {
        return get(column)
    }
}

Other Operators

In addition to filter operators, SQLite.swift defines a number of operators that can modify expression values with arithmetic, bitwise operations, and concatenation.

Other Infix Operators
Swift Types SQLite
+ Number -> Number +
- Number -> Number -
* Number -> Number *
/ Number -> Number /
% Int -> Int %
<< Int -> Int <<
>> Int -> Int >>
& Int -> Int &
` ` Int -> Int
+ String -> String `

Note: SQLite.swift also defines a bitwise XOR operator, ^, which expands the expression lhs ^ rhs to ~(lhs & rhs) & (lhs | rhs).

Other Prefix Operators
Swift Types SQLite
~ Int -> Int ~
- Number -> Number -

Core SQLite Functions

Many of SQLite’s core functions have been surfaced in and type-audited for SQLite.swift.

Note: SQLite.swift aliases the ?? operator to the ifnull function.

name ?? email // ifnull("name", "email")

Aggregate SQLite Functions

Most of SQLite’s aggregate functions have been surfaced in and type-audited for SQLite.swift.

Executing Arbitrary SQL

Though we recommend you stick with SQLite.swift’s type-safe system whenever possible, it is possible to simply and safely prepare and execute raw SQL statements via a Database connection using the following functions.

  • execute runs an arbitrary number of SQL statements as a convenience.

    db.execute(
    "BEGIN TRANSACTION;" +
    "CREATE TABLE users (" +
        "id INTEGER PRIMARY KEY NOT NULL," +
        "email TEXT UNIQUE NOT NULL," +
        "name TEXT" +
    ");" +
    "CREATE TABLE posts (" +
        "id INTEGER PRIMARY KEY NOT NULL," +
        "title TEXT NOT NULL," +
        "body TEXT NOT NULL," +
        "published_at DATETIME" +
    ");" +
    "PRAGMA user_version = 1;" +
    "COMMIT TRANSACTION;"
)

  • prepare prepares a single Statement object from a SQL string, optionally binds values to it (using the statement’s bind function), and returns the statement for deferred execution.

    let stmt = db.prepare("INSERT INTO users (email) VALUES (?)")

    Once prepared, statements may be executed using run, binding any unbound parameters.

    stmt.run("alice@mac.com")
db.lastChanges // -> {Some 1}

    Statements with results may be iterated over.

    let stmt = db.prepare("SELECT id, email FROM users")
for row in stmt {
    println("id: \(row[0]), email: \(row[1])")
    // id: Optional(1), email: Optional("alice@mac.com")
}

  • run prepares a single Statement object from a SQL string, optionally binds values to it (using the statement’s bind function), executes, and returns the statement.

    db.run("INSERT INTO users (email) VALUES (?)", "alice@mac.com")

  • scalar prepares a single Statement object from a SQL string, optionally binds values to it (using the statement’s bind function), executes, and returns the first value of the first row.

    db.scalar("SELECT count(*) FROM users") as Int

    Statements also have a scalar function, which can optionally re-bind values at execution.

    let stmt = db.prepare("SELECT count (*) FROM users")
stmt.scalar() as Int

Logging

We can log SQL using the database’s trace function.

#if DEBUG
    db.trace(println)
#endif