Exactamente. Tiene un límite, que puedes
ver en el manual de referencia:
Cita: The result is truncated to the maximum length that is given by the group_concat_max_len system variable, which has a default value of
1024. The value
can be set higher, although
the effective maximum length of the return value is constrained by the value of max_allowed_packet. The syntax to change the value of group_concat_max_len at runtime is as follows, where val is an unsigned integer:
Código SQL:
Ver originalSET [GLOBAL | SESSION] group_concat_max_len = val;
The return value is a nonbinary or binary string, depending on whether the arguments are nonbinary or binary strings. The result type is TEXT or BLOB unless group_concat_max_len is less than or equal to 512, in which case the result type is VARCHAR or VARBINARY.
Tambien peudes usar para este fin la función
CONCAT_WS().