mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-27 10:02:01 +00:00
238 lines
6.6 KiB
Markdown
238 lines
6.6 KiB
Markdown
# Operators
|
||
|
||
All operators are transformed to the corresponding functions at the query parsing stage, in accordance with their precedence and associativity.
|
||
Groups of operators are listed in order of priority (the higher it is in the list, the earlier the operator is connected to its arguments).
|
||
|
||
## Access Operators
|
||
|
||
`a[N]` Access to an element of an array; ` arrayElement(a, N) function`.
|
||
|
||
`a.N` – Access to a tuble element; `tupleElement(a, N)` function.
|
||
|
||
## Numeric Negation Operator
|
||
|
||
`-a` – The `negate (a)` function.
|
||
|
||
## Multiplication and Division Operators
|
||
|
||
`a * b` – The `multiply (a, b) function.`
|
||
|
||
`a / b` – The ` divide(a, b) function.`
|
||
|
||
`a % b` – The `modulo(a, b) function.`
|
||
|
||
## Addition and Subtraction Operators
|
||
|
||
`a + b` – The `plus(a, b) function.`
|
||
|
||
`a - b` – The `minus(a, b) function.`
|
||
|
||
## Comparison Operators
|
||
|
||
`a = b` – The `equals(a, b) function.`
|
||
|
||
`a == b` – The ` equals(a, b) function.`
|
||
|
||
`a != b` – The `notEquals(a, b) function.`
|
||
|
||
`a <> b` – The `notEquals(a, b) function.`
|
||
|
||
`a <= b` – The `lessOrEquals(a, b) function.`
|
||
|
||
`a >= b` – The `greaterOrEquals(a, b) function.`
|
||
|
||
`a < b` – The `less(a, b) function.`
|
||
|
||
`a > b` – The `greater(a, b) function.`
|
||
|
||
`a LIKE s` – The `like(a, b) function.`
|
||
|
||
`a NOT LIKE s` – The `notLike(a, b) function.`
|
||
|
||
`a BETWEEN b AND c` – The same as `a >= b AND a <= c.`
|
||
|
||
`a NOT BETWEEN b AND c` – The same as `a < b OR a > c.`
|
||
|
||
## Operators for Working With Data Sets
|
||
|
||
*See the section [IN operators](select.md#select-in-operators).*
|
||
|
||
`a IN ...` – The `in(a, b) function`
|
||
|
||
`a NOT IN ...` – The `notIn(a, b) function.`
|
||
|
||
`a GLOBAL IN ...` – The `globalIn(a, b) function.`
|
||
|
||
`a GLOBAL NOT IN ...` – The `globalNotIn(a, b) function.`
|
||
|
||
## Operator for Working With Dates and Times {#operators-datetime}
|
||
|
||
``` sql
|
||
EXTRACT(part FROM date);
|
||
```
|
||
|
||
Extracts a part from a given date. For example, you can retrieve a month from a given date, or a second from a time.
|
||
|
||
The `part` parameter specifies which part of the date to retrieve. The following values are available:
|
||
|
||
- `DAY` — The day of the month. Possible values: 1–31.
|
||
- `MONTH` — The number of a month. Possible values: 1–12.
|
||
- `YEAR` — The year.
|
||
- `SECOND` — The second. Possible values: 0–59.
|
||
- `MINUTE` — The minute. Possible values: 0–59.
|
||
- `HOUR` — The hour. Possible values: 0–23.
|
||
|
||
The `part` parameter is case-insensitive.
|
||
|
||
The `date` parameter specifies the date or the time to process. Either [Date](../data_types/date.md) or [DateTime](../data_types/datetime.md) type is supported.
|
||
|
||
Examples:
|
||
|
||
``` sql
|
||
SELECT EXTRACT(DAY FROM toDate('2017-06-15'));
|
||
SELECT EXTRACT(MONTH FROM toDate('2017-06-15'));
|
||
SELECT EXTRACT(YEAR FROM toDate('2017-06-15'));
|
||
```
|
||
|
||
In the following example we create a table and insert into it a value with the `DateTime` type.
|
||
|
||
``` sql
|
||
CREATE TABLE test.Orders
|
||
(
|
||
OrderId UInt64,
|
||
OrderName String,
|
||
OrderDate DateTime
|
||
)
|
||
ENGINE = Log;
|
||
```
|
||
|
||
``` sql
|
||
INSERT INTO test.Orders VALUES (1, 'Jarlsberg Cheese', toDateTime('2008-10-11 13:23:44'));
|
||
```
|
||
``` sql
|
||
SELECT
|
||
toYear(OrderDate) AS OrderYear,
|
||
toMonth(OrderDate) AS OrderMonth,
|
||
toDayOfMonth(OrderDate) AS OrderDay,
|
||
toHour(OrderDate) AS OrderHour,
|
||
toMinute(OrderDate) AS OrderMinute,
|
||
toSecond(OrderDate) AS OrderSecond
|
||
FROM test.Orders;
|
||
|
||
┌─OrderYear─┬─OrderMonth─┬─OrderDay─┬─OrderHour─┬─OrderMinute─┬─OrderSecond─┐
|
||
│ 2008 │ 10 │ 11 │ 13 │ 23 │ 44 │
|
||
└───────────┴────────────┴──────────┴───────────┴─────────────┴─────────────┘
|
||
```
|
||
|
||
You can see more examples in [tests](https://github.com/yandex/ClickHouse/blob/master/dbms/tests/queries/0_stateless/00619_extract.sql).
|
||
|
||
## Logical Negation Operator
|
||
|
||
`NOT a` The `not(a) function.`
|
||
|
||
## Logical AND Operator
|
||
|
||
`a AND b` – The`and(a, b) function.`
|
||
|
||
## Logical OR Operator
|
||
|
||
`a OR b` – The `or(a, b) function.`
|
||
|
||
## Conditional Operator
|
||
|
||
`a ? b : c` – The `if(a, b, c) function.`
|
||
|
||
Note:
|
||
|
||
The conditional operator calculates the values of b and c, then checks whether condition a is met, and then returns the corresponding value. If `b` or `C` is an [arrayJoin()](functions/array_join.md#functions_arrayjoin) function, each row will be replicated regardless of the "a" condition.
|
||
|
||
## Conditional Expression {#operator_case}
|
||
|
||
``` sql
|
||
CASE [x]
|
||
WHEN a THEN b
|
||
[WHEN ... THEN ...]
|
||
[ELSE c]
|
||
END
|
||
```
|
||
|
||
If `x` is specified, then `transform(x, [a, ...], [b, ...], c)` function is used. Otherwise – `multiIf(a, b, ..., c)`.
|
||
|
||
If there is no `ELSE c` clause in the expression, the default value is `NULL`.
|
||
|
||
The `transform` function does not work with `NULL`.
|
||
|
||
## Concatenation Operator
|
||
|
||
`s1 || s2` – The `concat(s1, s2) function.`
|
||
|
||
## Lambda Creation Operator
|
||
|
||
`x -> expr` – The `lambda(x, expr) function.`
|
||
|
||
The following operators do not have a priority, since they are brackets:
|
||
|
||
## Array Creation Operator
|
||
|
||
`[x1, ...]` – The `array(x1, ...) function.`
|
||
|
||
## Tuple Creation Operator
|
||
|
||
`(x1, x2, ...)` – The `tuple(x2, x2, ...) function.`
|
||
|
||
## Associativity
|
||
|
||
All binary operators have left associativity. For example, `1 + 2 + 3` is transformed to `plus(plus(1, 2), 3)`.
|
||
Sometimes this doesn't work the way you expect. For example, ` SELECT 4 > 2 > 3` will result in 0.
|
||
|
||
For efficiency, the `and` and `or` functions accept any number of arguments. The corresponding chains of `AND` and `OR` operators are transformed to a single call of these functions.
|
||
|
||
## Checking for `NULL`
|
||
|
||
ClickHouse supports the `IS NULL` and `IS NOT NULL` operators.
|
||
|
||
### IS NULL {#operator-is-null}
|
||
|
||
- For [Nullable](../data_types/nullable.md) type values, the `IS NULL` operator returns:
|
||
- `1`, if the value is `NULL`.
|
||
- `0` otherwise.
|
||
- For other values, the `IS NULL` operator always returns `0`.
|
||
|
||
```bash
|
||
:) SELECT x+100 FROM t_null WHERE y IS NULL
|
||
|
||
SELECT x + 100
|
||
FROM t_null
|
||
WHERE isNull(y)
|
||
|
||
┌─plus(x, 100)─┐
|
||
│ 101 │
|
||
└──────────────┘
|
||
|
||
1 rows in set. Elapsed: 0.002 sec.
|
||
```
|
||
|
||
|
||
### IS NOT NULL
|
||
|
||
- For [Nullable](../data_types/nullable.md) type values, the `IS NOT NULL` operator returns:
|
||
- `0`, if the value is `NULL`.
|
||
- `1` otherwise.
|
||
- For other values, the `IS NOT NULL` operator always returns `1`.
|
||
|
||
```bash
|
||
:) SELECT * FROM t_null WHERE y IS NOT NULL
|
||
|
||
SELECT *
|
||
FROM t_null
|
||
WHERE isNotNull(y)
|
||
|
||
┌─x─┬─y─┐
|
||
│ 2 │ 3 │
|
||
└───┴───┘
|
||
|
||
1 rows in set. Elapsed: 0.002 sec.
|
||
```
|
||
|
||
[Original article](https://clickhouse.yandex/docs/en/query_language/operators/) <!--hide-->
|