MYSQL相关

相同表字段更新

UPDATE hwy_km_stake_coordinate a
JOIN hwy_km_stake_coordinate_copy b ON a.h_way_no = b.h_way_no 
AND a.line_no = b.line_no 
AND a.r_sect_direct = b.r_sect_direct 
AND b.flag = 1 
SET a.coordinate = b.coordinate

修改表字段长度

ALTER TABLE maint_project  MODIFY COLUMN project_id  VARCHAR(255)

添加字段

alter table maint_project ADD `stake_middle` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '计算出的中间桩号';
alter table maint_project ADD  `lng_lat_start` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '开始桩号对应的经纬度';

修改字段是否为NULL

ALTER TABLE glyh.maint_project MODIFY COLUMN  `facility_name` varchar(64)  DEFAULT NULL COMMENT '设施名称'; -- 默认可为NULL
ALTER TABLE glyh.maint_project MODIFY COLUMN  `facility_name` varchar(64)  DEFAULT NOT NULL COMMENT '设施名称'; -- 默认可为NULL