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MySQL Types

SQLDelight column definitions are identical to regular MySQL column definitions but support an extra column constraint which specifies the Kotlin type of the column in the generated interface.

CREATE TABLE some_types (
  some_tiny_int TINYINT,             -- Retrieved as Int
  some_small_int SMALLINT,           -- Retrieved as Int
  some_medium_int MEDIUMINT,         -- Retrieved as Int
  some_integer INTEGER,              -- Retrieved as Int
  some_int INT,                      -- Retrieved as Int
  some_big_int BIGINT,               -- Retrieved as Long
  some_decimal DECIMAL,              -- Retrieved as Double
  some_dec DEC,                      -- Retrieved as Double
  some_fixed FIXED,                  -- Retrieved as Double
  some_numeric NUMERIC,              -- Retrieved as Double
  some_float FLOAT,                  -- Retrieved as Double
  some_real REAL,                    -- Retrieved as Double
  some_double_prec DOUBLE PRECISION, -- Retrieved as Double
  some_double DOUBLE,                -- Retrieved as Double
  some_date DATE,                    -- Retrieved as String
  some_time TIME,                    -- Retrieved as String
  some_datetime DATETIME,            -- Retrieved as String
  some_timestamp TIMESTAMP,          -- Retrieved as String
  some_year YEAR,                    -- Retrieved as String
  some_char CHAR,                    -- Retrieved as String
  some_varchar VARCHAR(16),          -- Retrieved as String
  some_tiny_text TINYTEXT,           -- Retrieved as String
  some_text TEXT,                    -- Retrieved as String
  some_medium_text MEDIUMTEXT,       -- Retrieved as String
  some_long_text LONGTEXT,           -- Retrieved as String
  some_enum ENUM,                    -- Retrieved as String
  some_set SET,                      -- Retrieved as String
  some_varbinary VARBINARY(8),       -- Retrieved as ByteArray
  some_blob BLOB(8, 8),              -- Retrieved as ByteArray
  some_binary BINARY,                -- Retrieved as ByteArray
  some_json JSON,                    -- Retrieved as String
  some_boolean BOOLEAN,              -- Retrieved as Boolean

Custom Column Types

If you'd like to retrieve columns as custom types you can specify a Kotlin type:

import kotlin.collections.List;

CREATE TABLE hockeyPlayer (
  cup_wins TEXT AS List<String> NOT NULL

However, creating the Database will require you to provide a ColumnAdapter which knows how to map between the database type and your custom type:

val listOfStringsAdapter = object : ColumnAdapter<List<String>, String> {
  override fun decode(databaseValue: String) =
    if (databaseValue.isEmpty()) {
    } else {
  override fun encode(value: List<String>) = value.joinToString(separator = ",")

val queryWrapper: Database = Database(
  driver = driver,
  hockeyPlayerAdapter = hockeyPlayer.Adapter(
    cup_winsAdapter = listOfStringsAdapter


As a convenience the SQLDelight runtime includes a ColumnAdapter for storing an enum as String data.


CREATE TABLE hockeyPlayer (
  position TEXT AS HockeyPlayer.Position
val queryWrapper: Database = Database(
  driver = driver,
  hockeyPlayerAdapter = HockeyPlayer.Adapter(
    positionAdapter = EnumColumnAdapter()

Custom Types in Migrations

If migrations are the schema's source of truth, you can also specify the exposed kotlin type when altering a table:

import kotlin.collection.List;

ALTER TABLE my_table
  ADD COLUMN new_column VARCHAR(8) AS List<String>;