Tuple ​

A Tuple groups a fixed number of values into one value. Each field has its own declared type. Fields can be addressed by position, and named fields can also be addressed by name.

Syntax ​

Tuple(T1, T2, ...)
Tuple(name1 T1, name2 T2, ...)

A tuple must contain at least one field. Either every field is named or every field is positional. Names must be nonempty, unique and case-sensitive.

Creating Tuples ​

Construct a tuple with tuple(...) or provide JSON array text with exactly the declared number of fields. A named tuple also accepts a JSON object with exactly its declared field names.

Every field is converted to its declared type. Use Nullable(T) for a field that can contain SQL NULL.

Referring to Tuple Elements ​

tuple_element(value, position) uses a positive one-based position within the declared field count. For named tuples, tuple_element(value, 'name') and dotted column access select the named field.

Examples ​

A positional tuple ​

SELECT tuple_element(CAST('[7,"Ada"]' AS Tuple(UInt32, String)), 2)
FORMAT csv;

"Ada"

Named records in a table ​

CREATE TABLE users(profile Tuple(id UInt64, name String));
INSERT INTO users VALUES ('{"id":7,"name":"Ada"}');

SELECT profile.id, profile.name,
       tuple_element(profile, 'name') AS selected_name
FROM users
FORMAT csv;

7,"Ada","Ada"

A nullable field ​

SELECT CAST('[7,null]' AS Tuple(UInt32, Nullable(String)))
FORMAT csv;

"[7,null]"

See Nested for arrays of named records and tuple functions for operations on tuple values.