| --- |
| { |
| "title": "ARRAY_LAST", |
| "language": "en", |
| "description": "Finds the last element in the array that satisfies the lambda expression. Finds the last element that satisfies the condition and returns it." |
| } |
| --- |
| |
| ## array_last |
| |
| <version since="2.0.0"> |
| |
| </version> |
| |
| ## Description |
| |
| Finds the last element in the array that satisfies the lambda expression. Finds the last element that satisfies the condition and returns it. |
| |
| ## Syntax |
| |
| ```sql |
| array_last(lambda, ARRAY<T> arr1, [ARRAY<T> arr2, ...]) |
| ``` |
| |
| ### Parameters |
| |
| - `lambda`:lambda expression used to define search conditions |
| - `arr1, arr2, ...`:ARRAY<T> type, arrays to search. Supports one or more array parameters. |
| |
| **Supported types for T:** |
| - Numeric types: TINYINT, SMALLINT, INT, BIGINT, LARGEINT, FLOAT, DOUBLE, DECIMAL |
| - String types: CHAR, VARCHAR, STRING |
| - Date and time types: DATE, DATETIME, DATEV2, DATETIMEV2 |
| - Boolean type: BOOLEAN |
| - IP types: IPV4, IPV6 |
| - Complex types: ARRAY, MAP, STRUCT |
| |
| ### Return Value |
| |
| Return type: T |
| |
| Return value meaning: |
| - Returns the last element in the array that satisfies the lambda expression |
| - NULL: if no element satisfies the condition, or if the input array is NULL |
| |
| Usage notes: |
| - The number of parameters in the lambda expression must match the number of array parameters |
| - If no element satisfies the condition, returns NULL |
| - Does not support NULL input parameters |
| - When there are multiple array parameters, all arrays must have the same length |
| - Lambda can use any scalar expression, but cannot use aggregate functions |
| - Lambda expressions can call other higher-order functions, but the return types must be compatible |
| - For null values in array elements: null elements will be passed to the lambda expression for processing, and lambda can check for null values |
| |
| **Query Examples:** |
| |
| Find the last element greater than or equal to 3 in a floating-point array: |
| ```sql |
| SELECT array_last(x -> x >= 3, [1.1, 2.2, 3.3, 4.4, 5.5]); |
| +----------------------------------------------------+ |
| | array_last(x -> x >= 3, [1.1, 2.2, 3.3, 4.4, 5.5]) | |
| +----------------------------------------------------+ |
| | 5.5 | |
| +----------------------------------------------------+ |
| ``` |
| |
| Find the last element with length greater than 2 in a string array: |
| ```sql |
| SELECT array_last(x -> length(x) > 2, ['a', 'bb', 'ccc', 'dddd', 'eeeee']); |
| +---------------------------------------------------------------------+ |
| | array_last(x -> length(x) > 2, ['a', 'bb', 'ccc', 'dddd', 'eeeee']) | |
| +---------------------------------------------------------------------+ |
| | eeeee | |
| +---------------------------------------------------------------------+ |
| ``` |
| |
| Empty array returns NULL: |
| ```sql |
| SELECT array_last(x -> x > 0, []); |
| +-------------------------------------+ |
| | array_last(x -> x > 0, []) | |
| +-------------------------------------+ |
| | NULL | |
| +-------------------------------------+ |
| ``` |
| |
| NULL input parameter will error: |
| ```sql |
| SELECT array_last(x -> x > 2, NULL); |
| ERROR 1105 (HY000): errCode = 2, detailMessage = lambda argument must be array but is NULL |
| |
| SELECT array_last(NULL); |
| ERROR 1105 (HY000): errCode = 2, detailMessage = Can not build function: 'array_last', expression: array_last(NULL), The 1st arg of array_filter must be lambda but is NULL |
| ``` |
| |
| Array containing null values, lambda can check for null: |
| ```sql |
| SELECT array_last(x -> x is not null, [null, 1, null, 3, null, 5]); |
| +-------------------------------------------------------------+ |
| | array_last(x -> x is not null, [null, 1, null, 3, null, 5]) | |
| +-------------------------------------------------------------+ |
| | 5 | |
| +-------------------------------------------------------------+ |
| ``` |
| |
| Multi-array search, find the last element where the first array is greater than the second array: |
| ```sql |
| SELECT array_last((x, y) -> x > y, [1, 2, 3, 4, 5], [1.1, 2.2, 3.3, 4.4, 5.5]); |
| +-------------------------------------------------------------------------+ |
| | array_last((x, y) -> x > y, [1, 2, 3, 4, 5], [1.1, 2.2, 3.3, 4.4, 5.5]) | |
| +-------------------------------------------------------------------------+ |
| | NULL | |
| +-------------------------------------------------------------------------+ |
| ``` |
| |
| Nested array search, find the last element where each sub-array length is greater than 2: |
| ```sql |
| SELECT array_last(x -> size(x) > 2, [[1,2],[3,4,5],[6],[7,8,9,10]]); |
| +--------------------------------------------------------------+ |
| | array_last(x -> size(x) > 2, [[1,2],[3,4,5],[6],[7,8,9,10]]) | |
| +--------------------------------------------------------------+ |
| | [7, 8, 9, 10] | |
| +--------------------------------------------------------------+ |
| ``` |
| |
| Error when parameter count is wrong: |
| ```sql |
| SELECT array_last(); |
| ERROR 1105 (HY000): errCode = 2, detailMessage = Can not found function 'array_last' which has 0 arity. Candidate functions are: [array_last(Expression, Expression...)] |
| ``` |
| |
| Error when the number of parameters in lambda expression doesn't match the number of array parameters: |
| ```sql |
| SELECT array_last(x -> x > 0, [1,2,3], [4,5,6], [7,8,9]); |
| ERROR 1105 (HY000): errCode = 2, detailMessage = lambda x -> (x > 0) arguments' size is not equal parameters' size |
| ``` |
| |
| Error when passing non-array type: |
| ```sql |
| SELECT array_last(x -> x > 0, 'not_an_array'); |
| ERROR 1105 (HY000): errCode = 2, detailMessage = Can not find the compatibility function signature: array_last(Expression, VARCHAR(12)) |
| ``` |
| |
| ### Keywords |
| |
| ARRAY, LAST, ARRAY_LAST |