MS SQL Server type mapping

The tables below list every MS SQL Server column type (Transact-SQL Data types) and the Kotlin type produced when the column is read into a DataFrame. Aliases are canonicalised by SQL Server at CREATE TABLE time, so DataFrame only ever sees the canonical type; they are listed in the same row as the canonical type for reference.

Column nullability is determined from the metadata provided by the JDBC driver. If the driver does not explicitly report a column as non-nullable, it is mapped to a nullable Kotlin type (Int? instead of Int).

Exact numeric types

Canonical	Aliases	DataFrame column type	Notes
`bit`	none	`Boolean`	Single-bit integer (`0`/`1`/`NULL`).
`tinyint`	none	`Int`	1-byte unsigned integer (`0..255`) — unusual: SQL Server's `tinyint` is unsigned.
`smallint`	none	`Int`	2-byte signed integer.
`int`	`integer`	`Int`	4-byte signed integer.
`bigint`	none	`Long`	8-byte signed integer.
`decimal(p,s)`	`dec(p,s)`, `numeric(p,s)`	`java.math.BigDecimal`	Fixed-point. `NUMERIC` and `DECIMAL` are stored identically.
`smallmoney`	none	`java.math.BigDecimal`	4-byte fixed-point money (`-214,748.3648 .. 214,748.3647`).
`money`	none	`java.math.BigDecimal`	8-byte fixed-point money.

Approximate numeric types

Canonical	Aliases	DataFrame column type	Notes
`float(n)`	`double precision` (n = 53)	`Double`	Default `n = 53`. `float(1..24)` maps to `Float`.
`real`	(alias) `float(24)`	`Float`	Explicit 4-byte float; equivalent to `float(24)`.

Date and time types

Canonical	Aliases	DataFrame column type	Notes
`date`	none	`java.util.Date`	Date only (`0001-01-01 .. 9999-12-31`).
`time(n)`	none	`java.sql.Time`	Time only with fractional-second precision (0–7).
`smalldatetime`	none	`kotlin.time.Instant`	Date + minute-precision time.
`datetime`	none	`kotlin.time.Instant`	Legacy date + time; ~3.33 ms precision.
`datetime2(n)`	none	`kotlin.time.Instant`	Modern date + time with fractional-second precision (0–7).
`datetimeoffset(n)`	none	`java.time.OffsetDateTime`	Date + time + explicit UTC offset.

Character strings

Canonical	Aliases	DataFrame column type	Notes
`char(n)`	`character(n)`	`String`	Fixed-length non-Unicode text (max `n = 8000`).
`varchar(n \| max)`	`character varying(n)`	`String`	Variable-length non-Unicode text.
`text`	none	`String`	Deprecated — use `varchar(max)`.
`nchar(n)`	`national character(n)`, `national char(n)`	`String`	Fixed-length UTF-16 text (max `n = 4000`).
`nvarchar(n \| max)`	`national character varying(n)`, `national char varying(n)`	`String`	Variable-length UTF-16 text.
`ntext`	`national text`	`String`	Deprecated — use `nvarchar(max)`.

Binary strings

Canonical	Aliases	DataFrame column type	Notes
`binary(n)`	none	`ByteArray`	Fixed-length binary (max `n = 8000`).
`varbinary(n \| max)`	`binary varying(n)`	`ByteArray`	Variable-length binary.
`image`	none	`ByteArray`	Deprecated — use `varbinary(max)`.

Row-version and identity

Canonical	Aliases	DataFrame column type	Notes
`rowversion`	`timestamp`	`ByteArray`	8-byte row-version. Note: SQL Server's `timestamp` is not a date/time type. Use `datetime2` instead.
`uniqueidentifier`	none	`String`	16-byte GUID, read as its 36-character string form.

Other types

Canonical	Aliases	DataFrame column type	Notes
`xml`	none	`String`	XML document text.
`sql_variant`	none	`Any`	Column holds a value of any base type; driver returns as generic `Object`.
`hierarchyid`	none	`ByteArray`	Hierarchical position (raw binary).
`geometry`	none	`ByteArray`	Planar spatial (WKB / EWKB).
`geography`	none	`ByteArray`	Geodetic spatial (WKB / EWKB).

MS SQL Server specifics

Unlike most databases, SQL Server's tinyint is unsigned (0..255), not signed.
The keyword TIMESTAMP in T-SQL is a synonym for rowversion (a row-version stamp), not a date/time type. Use datetime2 for wall-clock timestamps.
text, ntext, and image are deprecated; SQL Server documentation recommends varchar(max)/nvarchar(max)/varbinary(max) respectively.
float(n) with n <= 24 returns Float; n >= 25 returns Double. float alone means float(53) and returns Double. real is float(24) and returns Float.

Unsupported types

geometry, geography; read as raw WKB ByteArray.
hierarchyid; read as raw ByteArray.
sql_variant; read as generic Any.
cursor and table types cannot be columns; they only occur as procedure parameters.

09 September 2026