建表 或 修改表 給某字段默認值

解決問題：根據廠家編號分類 沒有填寫的廠家編號默認為一組 稱之為'其他'

建表給某字段 默認字符串

CREATE TABLE `t_device_list`  (
  `device_id` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '終端ID',
  `device_manufacturer_id` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT 'cs999999' COMMENT '終端廠商編號',
  `business_terminal` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT 'bt999999' COMMENT '業務終端(A:集中器，B:配變終端,C:二遙，D:三遙,E:其他)',
  `network_port` varchar(255) CHARACTER SET utf16le COLLATE utf16le_general_ci NULL DEFAULT NULL COMMENT '網管端口',
  PRIMARY KEY (`device_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '終端設備基本信息  不會變化的信息存儲於此表' ROW_FORMAT = Compact;

修改表 給某字段 默認字符串

alter table t_device_list alter column business_terminal set default 'bt999999';
alter table t_device_list alter column device_manufacturer_id set default 'cs999999';

建表給某字段 默認當前時間

CREATE TABLE `t_device_manufacturer`  (
  `id` int(20) NOT NULL AUTO_INCREMENT COMMENT '主鍵',
  `device_manufacturer_id` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '廠家id',
  `device_manufacturer_name` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '廠家名稱',
  `create_time` datetime(0) NULL DEFAULT NULL COMMENT '創建時間',
  `update_time` datetime(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP(0) COMMENT '更新時間',
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `index_id_name`(`device_manufacturer_id`, `device_manufacturer_name`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '廠家表' ROW_FORMAT = Compact;