LESCE','Syntax:\nCOALESCE(value,...)\n\nReturns the first non-NULL value in the list, or NULL if there are no\nnon-NULL values.\n\nThe return type of COALESCE() is the aggregated type of the argument\ntypes.\n\nURL: http://dev.mysql.com/doc/refman/5.7/en/comparison-operators.html\n\n','mysql> SELECT COALESCE(NULL,1);\n        -> 1\nmysql> SELECT COALESCE(NULL,NULL,NULL);\n        -> NULL\n','http://dev.mysql.com/doc/refman/5.7/en/comparison-operators.html');