ClickHouse Data Type

This section describes the data types of MRS ClickHouse.

For details about the ClickHouse data types, see ClickHouse Data Types.

**Table 1** ClickHouse data types
Category	Keyword	Data Type	Description
Data type	Int8	Int8	Value range: [–128, 127]
	Int16	Int16	Value range: [–32768, 32767]
	Int32	Int32	Value range: [–2147483648, 2147483647]
	Int64	Int64	Value range: [–9223372036854775808, 9223372036854775807]
Floating point type	Float32	Float	Similar to the Float type in the C programming language. A single-precision floating point number occupies four bytes in storage of a computer and is represented in 32-bit binary.
Floating point type	Float64	Double	Similar to the Double type in the C programming language. A double-precision floating point number occupies eight bytes in storage of a computer and is represented in 64-bit binary.
Decimal type	Decimal	Decimal	A signed fixed-point number that can ensure precision during addition, subtraction, and multiplication operations. The following formats are supported: Decimal(P, S) Decimal32(S) Decimal64(S) Decimal128(S) NOTE: P stands for precision. The valid range is [1:38]. It determines the number of decimal digits (including fractions) that can be contained. S stands for scale. The valid range is [0:P]. It determines the number of decimal places of a number.
String type	String	String	A string can be of any length. It can contain any set of bytes, including empty bytes. The String type can replace the VARCHAR, BLOB, and CLOB types in other DBMSs.
String type	FixedString	Fixed-length string	When the length of the data happens to be N bytes, using the FixedString type is more efficient than other types. In other cases, this may reduce efficiency. The following values can be effectively stored in columns of the FixedString type: IP address represented in binary (FixedString (16) for IPv6) Language code (ru_RU, en_US...) Currency code (USD, RUB...) Hash value represented in binary mode (FixedString (16) for MD5 and FixedString (32) for SHA256)
Time and date type	Date	Date	The value is stored in two bytes, indicating the date value since 1970-01-01 (unsigned) to the current date. The time zone information is not stored.
	DateTime	Timestamp	The value is a Unix timestamp stored in four bytes (unsigned). Value range of this type is the same as the Date type. The minimum value is 1970-01-01 00:00:00. The timestamp type value is accurate to second (no leap second). The system time zone will be used when the client or server is started.
	DateTime64	DateTime64	This type allows you to store a time value in date plus time format.
Boolean type	Boolean	Boolean	ClickHouse does not have a type to store Boolean values. You can use the UInt8 and limit the value to be 0 or 1.
Array type	Array	Array	Array(T) is an array consisting of T elements. T can be of any type, including the array type. However, multi-dimensional arrays are not recommended. ClickHouse has limited support for multi-dimensional arrays. For example, you cannot store multidimensional arrays in a MergeTree table.
Tuple type	Tuple	Tuple	Each element of Tuple(T1, T2, ...) is of different type from other elements. Tuples cannot be stored in tables (except memory tables). Tuples can be used for grouping temporary columns. You can use IN expressions and lambda functions with specific parameters to group temporary columns.
Domains data type	Domains	Domains	Domains types are implementation-specific types. IPv4 is a Domains type that is binary compatible with the UInt32 type and is used to store the value of an IPv4 address. It provides more compact binary storage while supporting recognition of more readable input and output formats. IPv6 is a Domains type that is binary compatible with the FixedString (16) type and is used to store the value of an IPv6 address. It provides more compact binary storage while supporting recognition of more readable input and output formats.
Enumerated type	Enum8	Enum8	Value range: [–128, 127] Enum stores the mapping of 'string'= integer, for example, Enum8('hello' = 1, 'world' = 2).
Enumerated type	Enum16	Enum16	Value range: [–32768, 32767]
Nullable type	Nullable	Nullable	Unless otherwise specified in the ClickHouse server configuration, NULL is the default value for any Nullable type. Nullable fields cannot be contained in table indexes. It can be stored together with the normal values of TypeName. For example, columns of the Nullable(Int8) type can store values of the Int8 type, while rows without values store NULL.
Nested type	nested	nested	A nested data structure is like a table within a cell of another table. The parameters (column name and type) of the nested data structure are specified in the same way as in the CREATE TABLE query. Each table row can correspond to any number of rows in a nested data structure. Example: Nested (Name1 Type1,Name2 Type2, ...)