8623cb232c
* CLICKHOUSE-4063: less manual html @ index.md * CLICKHOUSE-4063: recommend markdown="1" in README.md * CLICKHOUSE-4003: manually purge custom.css for now * CLICKHOUSE-4064: expand <details> before any print (including to pdf) * CLICKHOUSE-3927: rearrange interfaces/formats.md a bit * CLICKHOUSE-3306: add few http headers * Remove copy-paste introduced in #3392 * Hopefully better chinese fonts #3392 * get rid of tabs @ custom.css * Apply comments and patch from #3384 * Add jdbc.md to ToC and some translation, though it still looks badly incomplete * minor punctuation * Add some backlinks to official website from mirrors that just blindly take markdown sources * Do not make fonts extra light * find . -name '*.md' -type f | xargs -I{} perl -pi -e 's//g' {} * find . -name '*.md' -type f | xargs -I{} perl -pi -e 's/ sql/g' {} * Remove outdated stuff from roadmap.md * Not so light font on front page too * Refactor Chinese formats.md to match recent changes in other languages
2.1 KiB
Tuple(T1, T2, ...)
A tuple of elements, each having an individual type.
You can't store tuples in tables (other than Memory tables). They are used for temporary column grouping. Columns can be grouped when an IN expression is used in a query, and for specifying certain formal parameters of lambda functions. For more information, see the sections IN operators and Higher order functions.
Tuples can be the result of a query. In this case, for text formats other than JSON, values are comma-separated in brackets. In JSON formats, tuples are output as arrays (in square brackets).
Creating a tuple
You can use a function to create a tuple:
tuple(T1, T2, ...)
Example of creating a tuple:
:) SELECT tuple(1,'a') AS x, toTypeName(x)
SELECT
(1, 'a') AS x,
toTypeName(x)
┌─x───────┬─toTypeName(tuple(1, 'a'))─┐
│ (1,'a') │ Tuple(UInt8, String) │
└─────────┴───────────────────────────┘
1 rows in set. Elapsed: 0.021 sec.
Working with data types
When creating a tuple on the fly, ClickHouse automatically detects the type of each argument as the minimum of the types which can store the argument value. If the argument is NULL, the type of the tuple element is Nullable.
Example of automatic data type detection:
SELECT tuple(1, NULL) AS x, toTypeName(x)
SELECT
(1, NULL) AS x,
toTypeName(x)
┌─x────────┬─toTypeName(tuple(1, NULL))──────┐
│ (1,NULL) │ Tuple(UInt8, Nullable(Nothing)) │
└──────────┴─────────────────────────────────┘
1 rows in set. Elapsed: 0.002 sec.