MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
Adds a value to a comma-separated list of values and returns the result.
          This function and list_drop()
          can be useful for manipulating the value of system variables
          such as sql_mode and
          optimizer_switch that take a
          comma-separated list of values.
        
mysql>SELECT @@sql_mode;+----------------------------------------+ | @@sql_mode | +----------------------------------------+ | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES | +----------------------------------------+ mysql>SET @@sql_mode = sys.list_add(@@sql_mode, 'NO_ENGINE_SUBSTITUTION');mysql>SELECT @@sql_mode;+---------------------------------------------------------------+ | @@sql_mode | +---------------------------------------------------------------+ | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION | +---------------------------------------------------------------+ mysql>SET @@sql_mode = sys.list_drop(@@sql_mode, 'ONLY_FULL_GROUP_BY');mysql>SELECT @@sql_mode;+--------------------------------------------+ | @@sql_mode | +--------------------------------------------+ | STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION | +--------------------------------------------+