mirror of https://github.com/ClickHouse/ClickHouse.git synced 2024-12-02 04:22:03 +00:00

2021-10-20 01:42:05 +03:00

12 KiB

Raw Blame History

toc_priority	toc_title
38	Operators

Operators

ClickHouse transforms operators to their corresponding functions at the query parsing stage according to their priority, precedence, and associativity.

Access Operators

a[N] – Access to an element of an array. The arrayElement(a, N) function.

a.N – Access to a tuple element. The tupleElement(a, N) function.

Numeric Negation Operator

-a – The negate (a) function.

For tuple negation: tupleNegate.

Multiplication and Division Operators

a * b – The multiply (a, b) function.

For multiplying tuple by number: tupleMultiplyByNumber, for scalar profuct: dotProduct.

a / b – The divide(a, b) function.

For dividing tuple by number: tupleDivideByNumber.

a % b – The modulo(a, b) function.

Addition and Subtraction Operators

a + b – The plus(a, b) function.

For tuple addiction: tuplePlus.

a - b – The minus(a, b) function.

For tuple subtraction: tupleMinus.

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 ILIKE s – The ilike(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 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.

Operators for Working with Dates and Times

EXTRACT

EXTRACT(part FROM date);

Extract parts 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 or DateTime type is supported.

Examples:

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.

CREATE TABLE test.Orders
(
    OrderId UInt64,
    OrderName String,
    OrderDate DateTime
)
ENGINE = Log;

INSERT INTO test.Orders VALUES (1, 'Jarlsberg Cheese', toDateTime('2008-10-11 13:23:44'));

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.

INTERVAL

Creates an Interval-type value that should be used in arithmetical operations with Date and DateTime-type values.

Types of intervals:

SECOND
MINUTE
HOUR
DAY
WEEK
MONTH
QUARTER
YEAR

You can also use a string literal when setting the INTERVAL value. For example, INTERVAL 1 HOUR is identical to the INTERVAL '1 hour' or INTERVAL '1' hour.

!!! warning "Warning" Intervals with different types can’t be combined. You can’t use expressions like INTERVAL 4 DAY 1 HOUR. Specify intervals in units that are smaller or equal to the smallest unit of the interval, for example, INTERVAL 25 HOUR. You can use consecutive operations, like in the example below.

Examples:

SELECT now() AS current_date_time, current_date_time + INTERVAL 4 DAY + INTERVAL 3 HOUR;

┌───current_date_time─┬─plus(plus(now(), toIntervalDay(4)), toIntervalHour(3))─┐
│ 2020-11-03 22:09:50 │                                    2020-11-08 01:09:50 │
└─────────────────────┴────────────────────────────────────────────────────────┘

SELECT now() AS current_date_time, current_date_time + INTERVAL '4 day' + INTERVAL '3 hour';

┌───current_date_time─┬─plus(plus(now(), toIntervalDay(4)), toIntervalHour(3))─┐
│ 2020-11-03 22:12:10 │                                    2020-11-08 01:12:10 │
└─────────────────────┴────────────────────────────────────────────────────────┘

SELECT now() AS current_date_time, current_date_time + INTERVAL '4' day + INTERVAL '3' hour;

┌───current_date_time─┬─plus(plus(now(), toIntervalDay('4')), toIntervalHour('3'))─┐
│ 2020-11-03 22:33:19 │                                        2020-11-08 01:33:19 │
└─────────────────────┴────────────────────────────────────────────────────────────┘

You can work with dates without using INTERVAL, just by adding or subtracting seconds, minutes, and hours. For example, an interval of one day can be set by adding 60*60*24.

!!! note "Note" The INTERVAL syntax or addDays function are always preferred. Simple addition or subtraction (syntax like now() + ...) doesn't consider time settings. For example, daylight saving time.

Examples:

SELECT toDateTime('2014-10-26 00:00:00', 'Europe/Moscow') AS time, time + 60 * 60 * 24 AS time_plus_24_hours, time + toIntervalDay(1) AS time_plus_1_day;

┌────────────────time─┬──time_plus_24_hours─┬─────time_plus_1_day─┐
│ 2014-10-26 00:00:00 │ 2014-10-26 23:00:00 │ 2014-10-27 00:00:00 │
└─────────────────────┴─────────────────────┴─────────────────────┘

See Also

Interval data type
toInterval type conversion functions

Logical AND Operator

Syntax SELECT a AND b — calculates logical conjunction of a and b with the function and.

Logical OR Operator

Syntax SELECT a OR b — calculates logical disjunction of a and b with the function or.

Logical Negation Operator

Syntax SELECT NOT a — calculates logical negation of a with the function not.

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() function, each row will be replicated regardless of the “a” condition.

Conditional Expression

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 does not 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 into a single call of these functions.

Checking for `NULL`

ClickHouse supports the IS NULL and IS NOT NULL operators.

IS NULL

For Nullable 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.

Can be optimized by enabling the optimize_functions_to_subcolumns setting. With optimize_functions_to_subcolumns = 1 the function reads only null subcolumn instead of reading and processing the whole column data. The query SELECT n IS NULL FROM table transforms to SELECT n.null FROM TABLE.

SELECT x+100 FROM t_null WHERE y IS NULL

┌─plus(x, 100)─┐
│          101 │
└──────────────┘

IS NOT NULL

For Nullable 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.

SELECT * FROM t_null WHERE y IS NOT NULL

┌─x─┬─y─┐
│ 2 │ 3 │
└───┴───┘

Can be optimized by enabling the optimize_functions_to_subcolumns setting. With optimize_functions_to_subcolumns = 1 the function reads only null subcolumn instead of reading and processing the whole column data. The query SELECT n IS NOT NULL FROM table transforms to SELECT NOT n.null FROM TABLE.

12 KiB Raw Blame History Unescape Escape

Operators

Access Operators

Numeric Negation Operator

Multiplication and Division Operators

Addition and Subtraction Operators

Comparison Operators

Operators for Working with Data Sets

Operators for Working with Dates and Times

EXTRACT

INTERVAL

Logical AND Operator

Logical OR Operator

Logical Negation Operator

Conditional Operator

Conditional Expression

Concatenation Operator

Lambda Creation Operator

Array Creation Operator

Tuple Creation Operator

Associativity

Checking for NULL

IS NULL

IS NOT NULL

12 KiB

Raw Blame History

Checking for `NULL`