Group_concat() | @sskaje

By @sskaje
Link: https://sskaje.me/2014/02/mysql-hive-presto-impala-transposition/

Rows to Columns

Rows to Comma Separated String

FROM:
+-----+-----+
| uid | tag |
+-----+-----+
|   1 |   1 |
|   1 |   2 |
|   1 |   3 |
|   2 |   1 |
|   2 |   4 |
|   3 |   5 |
+-----+-----+
TO:
+-----+----------+
| uid | tag_list |
+-----+----------+
|   1 | 1,2,3    |
|   2 | 1,4      |
|   3 | 5        |
+-----+----------+

FROM:

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

| uid | tag |

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

| 1 | 1 |

| 1 | 2 |

| 1 | 3 |

| 2 | 1 |

| 2 | 4 |

| 3 | 5 |

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

TO:

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

| uid | tag_list |

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

| 1 | 1,2,3 |

| 2 | 1,4 |

| 3 | 5 |

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

MySQL

Use GROUP_CONCAT(). This function also works in Infobright.

MySQL/Hive/Presto/Impala Transposition by @sskaje: https://sskaje.me/2014/02/mysql-hive-presto-impala-transposition/

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