ClickHouse Data Type

Updated on 2024-07-19 GMT+08:00

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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 C, a single-precision floating point number occupies 4 bytes in storage of a computer and is described in 32-bit binary mode.
Floating point type	Float64	Double	Similar to the Double type in the C language, a double-precision floating point number occupies eight bytes in the machine and is described in 64-bit binary mode.
Decimal type	Decimal	Decimal	A signed fixed-point number that can maintain precision during addition, subtraction, and multiplication operations. The following formats are supported: Decimal(P, S) Decimal32(S) Decimal64(S) Decimal128(S) NOTE: P: precision. Valid range: [1:38]. It determines the number of decimal digits (including fractions) that can be contained. S: scale. The value ranges from 0 to P, which determines the number of decimal places in the decimal part of a number.
String type	String	String	The character string can be of any length. It can contain any set of bytes, including empty bytes. Therefore, 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, the FixedString type is efficient. In other cases, this may reduce efficiency. Examples of values that can be effectively stored in columns of the FixedString type: IP address represented in binary (IPv6 uses FixedString (16)) Language code (ru_RU, en_US...) Currency code 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 from 1970-01-01 (unsigned) to the current time. The time zone information is not stored in the date.
	DateTime	Timestamp	Stores Unix timestamps in four bytes (unsigned). Allows values within the same range as the date type to be stored. The minimum value is 1970-01-01 00:00:00. The timestamp type value is accurate to second (no leap second). The time zone uses the system time zone when the client or server is started.
	DateTime64	DateTime64	This type allows you to store a time value in the form of date plus time.
Boolean type	Boolean	Boolean	ClickHouse does not have a separate type to store Boolean values. The UInt8 type can be used. The value can be 0 or 1.
Array type	Array	Array	Array(T): array consisting of T-type elements. T The value 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	Tuple(T1, T2, ...), tuple, in which each element has a separate type and tuples cannot be stored in tables (except memory tables). They can be used for temporary column grouping. In a query, IN expressions and lambda functions with specific parameters can be used 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 domain 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 value 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. 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, ...)