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Array Functions and Operators

Array Operators

  • =

    Description: Specifies whether two arrays are equal.

    For example:

    mogdb=# 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:

    mogdb=# 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:

    mogdb=# 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:

    mogdb=# 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:

    mogdb=# 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:

    mogdb=# SELECT ARRAY[1,4,3] >= ARRAY[1,4,3] AS RESULT;
     result 
    --------
     t
    (1 row)
  • @>

    Description: Specifies whether an array contains another.

    For example:

    mogdb=# 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:

    mogdb=# 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:

    mogdb=# SELECT ARRAY[1,4,3] && ARRAY[2,1] AS RESULT;
     result 
    --------
     t
    (1 row)
  • ||

    Description: Array-to-array concatenation

    For example:

    mogdb=# SELECT ARRAY[1,2,3] || ARRAY[4,5,6] AS RESULT;
        result     
    ---------------
     {1,2,3,4,5,6}
    (1 row)
    mogdb=# 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:

    mogdb=# SELECT 3 || ARRAY[4,5,6] AS RESULT;
      result   
    -----------
     {3,4,5,6}
    (1 row)
  • ||

    Description: Array-to-element concatenation

    For example:

    mogdb=# 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:

    mogdb=# 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:

    mogdb=# 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:

    mogdb=# SELECT array_cat(ARRAY[1,2,3], ARRAY[4,5]) AS RESULT;
       result    
    -------------
     {1,2,3,4,5}
    (1 row)
        
    mogdb=# 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:

    mogdb=# SELECT array_ndims(ARRAY[[1,2,3], [4,5,6]]) AS RESULT;
     result 
    --------
          2
    (1 row)
  • array_dims(anyarray)

    Description: Returns the low-order flag bits and high-order flag bits of each dimension in an array.

    Return type: text

    For example:

    mogdb=# 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. int is the requested array dimension.

    Return type: int

    For example:

    mogdb=# SELECT array_length(array[1,2,3], 1) AS RESULT;
     result 
    --------
          3
    (1 row)
        
    mogdb=# SELECT array_length(array[[1,2,3],[4,5,6]], 2) AS RESULT;
     result
    --------
          3
    (1 row)
  • array_lower(anyarray, int)

    Description: Returns lower bound of the requested array dimension. int is the requested array dimension.

    Return type: int

    For example:

    mogdb=# 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. int is the requested array dimension.

    Return type: int

    For example:

    mogdb=# 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:

    mogdb=# 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:

    mogdb=# SELECT string_to_array('xx~^~yy~^~zz', '~^~', 'yy') AS RESULT;
        result    
    --------------
     {xx,NULL,zz}
    (1 row)
    mogdb=# 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:

    mogdb=# 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.