PostgreSQL 7.4 Documentation
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# 9.14. Array Functions and Operators

Table 9-41 shows the operators available for `array` types.

Table 9-41. `array` Operators

Operator | Description | Example | Result
--- | --- | --- | ---
= | equal | ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3] | t
<> | not equal | ARRAY[1,2,3] <> ARRAY[1,2,4] | t
< | less than | ARRAY[1,2,3] < ARRAY[1,2,4] | t
> | greater than | ARRAY[1,4,3] > ARRAY[1,2,4] | t
<= | less than or equal | ARRAY[1,2,3] <= ARRAY[1,2,3] | t
>= | greater than or equal | ARRAY[1,4,3] >= ARRAY[1,4,3] | t
|| | array-to-array concatenation | ARRAY[1,2,3] || ARRAY[4,5,6] | {1,2,3,4,5,6}
|| | array-to-array concatenation | ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]] | {{1,2,3},{4,5,6},{7,8,9}}
|| | element-to-array concatenation | 3 || ARRAY[4,5,6] | {3,4,5,6}
|| | array-to-element concatenation | ARRAY[4,5,6] || 7 | {4,5,6,7}

See Section 8.10 for more details about array operator behavior.

Table 9-42 shows the functions available for use with array types. See Section 8.10 for more discussion and examples for the use of these functions.

Table 9-42. `array` Functions

Function | Return Type | Description | Example | Result
--- | --- | --- | --- | ---
`array_cat` (`anyarray`, `anyarray`) | `anyarray` | concatenate two arrays, returning NULL for NULL inputs | array_cat(ARRAY[1,2,3], ARRAY[4,5]) | {1,2,3,4,5}
`array_append` (`anyarray`, `anyelement`) | `anyarray` | append an element to the end of an array, returning NULL for NULL inputs | array_append(ARRAY[1,2], 3) | {1,2,3}
`array_prepend` (`anyelement`, `anyarray`) | `anyarray` | append an element to the beginning of an array, returning NULL for NULL inputs | array_prepend(1, ARRAY[2,3]) | {1,2,3}
`array_dims` (`anyarray`) | `text` | returns a text representation of array dimension lower and upper bounds, generating an ERROR for NULL inputs | array_dims(array[[1,2,3], [4,5,6]]) | [1:2][1:3]
`array_lower` (`anyarray`, `integer`) | `integer` | returns lower bound of the requested array dimension, returning NULL for NULL inputs | array_lower(array_prepend(0, ARRAY[1,2,3]), 1) | 0
`array_upper` (`anyarray`, `integer`) | `integer` | returns upper bound of the requested array dimension, returning NULL for NULL inputs | array_upper(ARRAY[1,2,3,4], 1) | 4
`array_to_string` (`anyarray`, `text`) | `text` | concatenates array elements using provided delimiter, returning NULL for NULL inputs | array_to_string(array[1, 2, 3], '~^~') | 1~^~2~^~3
`string_to_array` (`text`, `text`) | `text[]` | splits string into array elements using provided delimiter, returning NULL for NULL inputs | string_to_array( 'xx~^~yy~^~zz', '~^~') | {xx,yy,zz}

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