Syntax

    2. mysql> set enable_vectorized_engine=true;
    4. mysql> select k1, k2, array_join(k2, '_', 'null') from array_test order by k1;
    5. +------+-----------------------------+------------------------------------+
    6. | k1   | k2                          | array_join(`k2`, '_', 'null')      |
    7. +------+-----------------------------+------------------------------------+
    8. |  1   | [1, 2, 3, 4, 5]             | 1_2_3_4_5                          |
    9. |  2   | [6, 7, 8]                   | 6_7_8                              |
    10. |  3   | []                          |                                    |
    11. |  4   | NULL                        | NULL                               |
    12. |  5   | [1, 2, 3, 4, 5, 4, 3, 2, 1] | 1_2_3_4_5_4_3_2_1                  |
    13. |  7   | [4, 5, 6, NULL, NULL]       | 4_5_6_null_null                    |
    14. +------+-----------------------------+------------------------------------+
    17. +------+-----------------------------------+------------------------------------+
    18. | k1   | k2                                | array_join(`k2`, '_', 'null')      |
    19. +------+-----------------------------------+------------------------------------+
    20. |  1   | ['a', 'b', 'c', 'd']              | a_b_c_d                            |
    21. |  2   | ['e', 'f', 'g', 'h']              | e_f_g_h                            |
    22. |  3   | [NULL, 'a', NULL, 'b', NULL, 'c'] | null_a_null_b_null_c               |
    23. |  4   | ['d', 'e', NULL, ' ']             | d_e_null_                          |
    24. |  5   | [' ', NULL, 'f', 'g']             |  _null_f_g                         |
    25. +------+-----------------------------------+------------------------------------+
    27. mysql> select k1, k2, array_join(k2, '_') from array_test order by k1;
    28. +------+-----------------------------+----------------------------+
    29. | k1   | k2                          | array_join(`k2`, '_')      |
    30. |  1   | [1, 2, 3, 4, 5]             | 1_2_3_4_5                  |
    31. |  2   | [6, 7, 8]                   | 6_7_8                      |
    33. |  4   | NULL                        | NULL                       |
    34. |  5   | [1, 2, 3, 4, 5, 4, 3, 2, 1] | 1_2_3_4_5_4_3_2_1          |
    35. |  6   | [1, 2, 3, NULL]             | 1_2_3                      |
    36. |  7   | [4, 5, 6, NULL, NULL]       | 4_5_6                      |
    37. +------+-----------------------------+----------------------------+
    39. mysql> select k1, k2, array_join(k2, '_') from array_test01 order by k1;
    40. +------+-----------------------------------+----------------------------+
    41. | k1   | k2                                | array_join(`k2`, '_')      |
    42. +------+-----------------------------------+----------------------------+
    43. |  1   | ['a', 'b', 'c', 'd']              | a_b_c_d                    |
    44. |  2   | ['e', 'f', 'g', 'h']              | e_f_g_h                    |
    45. |  3   | [NULL, 'a', NULL, 'b', NULL, 'c'] | a_b_c                      |
    46. |  4   | ['d', 'e', NULL, ' ']             | d_e_                       |
    47. +------+-----------------------------------+----------------------------+