array_join

Concatenates the elements of an array into a string.

Syntax

array_join(array, sep[, null_replace_str])

Parameters

• array: the array whose elements you want to concatenate. Only the ARRAY data type is supported.

• sep: the delimiter that is used to separate the concatenated array elements. Only the VARCHAR data type is supported.

• null_replace_str: the string that is used to substitute NULL values. Only the VARCHAR data type is supported.

Return value

Returns a value of the VARCHAR data type.

Usage notes

• The value of the array parameter must be a one-dimensional array.

• The array parameter does not support DECIMAL values.

• If you set the sep parameter to NULL, the return value is NULL.

• If you do not specify the null_replace_str parameter, NULL values are discarded.

• If you set the null_replace_str parameter to NULL, the return value is NULL.

Examples

Example 1: Concatenate the elements of an array. In this example, the NULL value in the array is discarded, and the concatenated array elements are separated by underscores (_).

mysql> select array_join([1, 3, 5, null], '_');

+-------------------------------+

| array_join([1,3,5,NULL], '_') |

+-------------------------------+

| 1_3_5                         |

+-------------------------------+

Example 2: Concatenate the elements of an array. In this example, the NULL value in the array is substituted with NULL strings, and the concatenated array elements are separated by underscores (_).

mysql> select array_join([1, 3, 5, null], '_', 'NULL');

+---------------------------------------+

| array_join([1,3,5,NULL], '_', 'NULL') |

+---------------------------------------+

| 1_3_5_NULL                            |

+---------------------------------------+