max_allowed_packet
http://dev.mysql.com/doc/refman/5.7/en/comparison-operators.html#function_in
SELECT val1 FROM tbl1 WHERE val1 IN (1,2,'a');
The number of values in the IN
list is only limited by the max_allowed_packet
value.
http://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_max_allowed_packet
You must increase this value if you are using large BLOB
columns or long strings. It should be as big as the largest BLOB
you want to use. The protocol limit for max_allowed_packet
is 1GB. The value should be a multiple of 1024; nonmultiples are rounded down to the nearest multiple.