mysql coalesce函数与 ifnull 函数对照
mysql coalesce函数与 ifnull 函数对比
# coalesce: 联合，合并。返回传入的参数中第一个非null的值 SELECT COALESCE (NULL, NULL, 1, 2); # 如果只有两个参数和IFNULL用法一样, 1 , 1 , 1 , NULL SELECT IFNULL(NULL, 1) as ifnull, COALESCE (NULL, 1) as coalesceTwo, COALESCE (NULL, NULL, 1, 2) as coalesceFour, COALESCE (NULL, NULL, NULL, NULL) as coalesceAllNull;