Lu, Huayi
a24ca60074
Reviewed-by: Hasko, Vladimir <vladimir.hasko@t-systems.com> Co-authored-by: Lu, Huayi <luhuayi@huawei.com> Co-committed-by: Lu, Huayi <luhuayi@huawei.com>
53 KiB
Array Functions and Operators
Array Operators
- =
Description: Specifies whether two arrays are equal.
For example:
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SELECT ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3] AS RESULT ; result -------- t (1 row)
- <>
Description: Specifies whether two arrays are not equal.
For example:
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SELECT ARRAY[1,2,3] <> ARRAY[1,2,4] AS RESULT; result -------- t (1 row)
- <
Description: Specifies whether an array is less than another.
For example:
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SELECT ARRAY[1,2,3] < ARRAY[1,2,4] AS RESULT; result -------- t (1 row)
- >
Description: Specifies whether an array is greater than another.
For example:
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SELECT ARRAY[1,4,3] > ARRAY[1,2,4] AS RESULT; result -------- t (1 row)
- <=
Description: Specifies whether an array is less than another.
For example:
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SELECT ARRAY[1,2,3] <= ARRAY[1,2,3] AS RESULT; result -------- t (1 row)
- >=
Description: Specifies whether an array is greater than or equal to another.
For example:
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SELECT ARRAY[1,4,3] >= ARRAY[1,4,3] AS RESULT; result -------- t (1 row)
- @>
Description: Specifies whether an array contains another.
For example:
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SELECT ARRAY[1,4,3] @> ARRAY[3,1] AS RESULT; result -------- t (1 row)
- <@
Description: Specifies whether an array is contained in another.
For example:
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SELECT ARRAY[2,7] <@ ARRAY[1,7,4,2,6] AS RESULT; result -------- t (1 row)
- &&
Description: Specifies whether an array overlaps another (have common elements).
For example:
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SELECT ARRAY[1,4,3] && ARRAY[2,1] AS RESULT; result -------- t (1 row)
- ||
Description: Array-to-array concatenation
For example:
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SELECT ARRAY[1,2,3] || ARRAY[4,5,6] AS RESULT; result --------------- {1,2,3,4,5,6} (1 row)
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SELECT ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]] AS RESULT; result --------------------------- {{1,2,3},{4,5,6},{7,8,9}} (1 row)
- ||
Description: Element-to-array concatenation
For example:
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SELECT 3 || ARRAY[4,5,6] AS RESULT; result ----------- {3,4,5,6} (1 row)
- ||
Description: Array-to-element concatenation
For example:
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SELECT ARRAY[4,5,6] || 7 AS RESULT; result ----------- {4,5,6,7} (1 row)
Array comparisons compare the array contents element-by-element, using the default B-tree comparison function for the element data type. In multidimensional arrays, the elements are accessed in row-major order. If the contents of two arrays are equal but the dimensionality is different, the first difference in the dimensionality information determines the sort order.
Array Functions
- array_append(anyarray, anyelement)
Description: Appends an element to the end of an array, and only supports dimension-1 arrays.
Return type: anyarray
For example:
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SELECT array_append(ARRAY[1,2], 3) AS RESULT; result --------- {1,2,3} (1 row)
- array_prepend(anyelement, anyarray)
Description: Appends an element to the beginning of an array, and only supports dimension-1 arrays.
Return type: anyarray
For example:
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SELECT array_prepend(1, ARRAY[2,3]) AS RESULT; result --------- {1,2,3} (1 row)
- array_cat(anyarray, anyarray)
Description: Concatenates two arrays, and supports multi-dimensional arrays.
Return type: anyarray
For example:
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SELECT array_cat(ARRAY[1,2,3], ARRAY[4,5]) AS RESULT; result ------------- {1,2,3,4,5} (1 row) SELECT array_cat(ARRAY[[1,2],[4,5]], ARRAY[6,7]) AS RESULT; result --------------------- {{1,2},{4,5},{6,7}} (1 row)
- array_ndims(anyarray)
Description: Returns the number of dimensions of the array.
Return type: int
For example:
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SELECT array_ndims(ARRAY[[1,2,3], [4,5,6]]) AS RESULT; result -------- 2 (1 row)
- array_dims(anyarray)
Description: Returns a text representation of array's dimensions.
Return type: text
For example:
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SELECT array_dims(ARRAY[[1,2,3], [4,5,6]]) AS RESULT; result ------------ [1:2][1:3] (1 row)
- array_length(anyarray, int)
Description: Returns the length of the requested array dimension.
Return type: int
For example:
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SELECT array_length(array[1,2,3], 1) AS RESULT; result -------- 3 (1 row)
- array_lower(anyarray, int)
Description: Returns lower bound of the requested array dimension.
Return type: int
For example:
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SELECT array_lower('[0:2]={1,2,3}'::int[], 1) AS RESULT; result -------- 0 (1 row)
- array_upper(anyarray, int)
Description: Returns upper bound of the requested array dimension.
Return type: int
For example:
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SELECT array_upper(ARRAY[1,8,3,7], 1) AS RESULT; result -------- 4 (1 row)
- array_to_string(anyarray, text [, text])
Description: Uses the first text as the new delimiter and the second text to replace NULL values.
Return type: text
For example:
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SELECT array_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*') AS RESULT; result ----------- 1,2,3,*,5 (1 row)
- string_to_array(text, text [, text])
Description: Uses the second text as the new delimiter and the third text as the substring to be replaced by NULL values. A substring can be replaced by NULL values only when it is the same as the third text.
Return type: text[]
For example:
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SELECT string_to_array('xx~^~yy~^~zz', '~^~', 'yy') AS RESULT; result -------------- {xx,NULL,zz} (1 row) SELECT string_to_array('xx~^~yy~^~zz', '~^~', 'y') AS RESULT; result ------------ {xx,yy,zz} (1 row)
- unnest(anyarray)
Description: Expands an array to a set of rows.
Return type: setof anyelement
For example:
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SELECT unnest(ARRAY[1,2]) AS RESULT; result -------- 1 2 (2 rows)
In string_to_array, if the delimiter parameter is NULL, each character in the input string will become a separate element in the resulting array. If the delimiter is an empty string, then the entire input string is returned as a one-element array. Otherwise the input string is split at each occurrence of the delimiter string.
In string_to_array, if the null-string parameter is omitted or NULL, none of the substrings of the input will be replaced by NULL.
In array_to_string, if the null-string parameter is omitted or NULL, any null elements in the array are simply skipped and not represented in the output string.