group_concat

description

Syntax

VARCHAR GROUP_CONCAT(VARCHAR str[, VARCHAR sep])

This function is an aggregation function similar to sum (), and group_concat links multiple rows of results in the result set to a string. The second parameter, sep, is a connection symbol between strings, which can be omitted. This function usually needs to be used with group by statements.

example

  1. mysql> select value from test;
  2. +-------+
  3. | value |
  4. +-------+
  5. | a     |
  6. | b     |
  7. | c     |
  8. +-------+
  10. mysql> select GROUP_CONCAT(value) from test;
  11. +-----------------------+
  12. | GROUP_CONCAT(`value`) |
  13. +-----------------------+
  14. | a, b, c               |
  15. +-----------------------+
  17. mysql> select GROUP_CONCAT(value, " ") from test;
  18. +----------------------------+
  19. | GROUP_CONCAT(`value`, ' ') |
  20. +----------------------------+
  21. | a b c                      |
  22. +----------------------------+
  24. mysql> select GROUP_CONCAT(value, NULL) from test;
  25. +----------------------------+
  26. | GROUP_CONCAT(`value`, NULL)|
  27. +----------------------------+
  28. | NULL                       |
  29. +----------------------------+

keyword

GROUP_CONCAT,GROUP,CONCAT