Mysql 增加主键或者修改主键的sql语句操作

添加表字段

alter table table1 add transactor varchar(10) not Null;
alter table table1 add id int unsigned not Null auto_increment primary key

修改某个表的字段类型及指定为空或非空

alter table 表名称 change 字段名称 字段名称 字段类型 [是否允许非空];

alter table 表名称 modify 字段名称 字段类型 [是否允许非空];

alter table 表名称 modify 字段名称 字段类型 [是否允许非空];

修改某个表的字段名称及指定为空或非空

alter table 表名称 change 字段原名称 字段新名称 字段类型 [是否允许非空

删除某一字段

ALTER TABLE mytable DROP 字段 名;

添加唯一键

ALTER TABLE `test2` ADD UNIQUE ( `userid`)

修改主键

ALTER TABLE `test2` DROP PRIMARY KEY ,ADD PRIMARY KEY ( `id` )

增加索引

ALTER TABLE `test2` ADD INDEX ( `id` )
ALTER TABLE `category ` MODIFY COLUMN `id` int(11) NOT NULL AUTO_INCREMENT FIRST ,ADD PRIMARY KEY (`id`);

修改主键的sql语句块如下

mailbox 表新增字段

DROP PROCEDURE IF EXISTS mailbox_column_update;
CREATE PROCEDURE mailbox_column_update() BEGIN
 -- 新增删除标志列
 IF NOT EXISTS(SELECT 1 FROM information_schema.COLUMNS WHERE TABLE_SCHEMA='cbs' AND table_name='mailbox' AND COLUMN_NAME='delete_flag') THEN
   ALTER TABLE mailbox ADD delete_flag int DEFAULT 2 NOT NULL;
 END IF;
 -- 新增删除日期列
 IF NOT EXISTS(SELECT 1 FROM information_schema.COLUMNS WHERE TABLE_SCHEMA='cbs' AND table_name='mailbox' AND COLUMN_NAME='delete_date') THEN
   ALTER TABLE mailbox ADD delete_date int DEFAULT 0 NOT NULL;
 END IF;
 -- 如果存在字段account_mail，则修改字段长度
 IF EXISTS(SELECT 1 FROM information_schema.COLUMNS WHERE TABLE_SCHEMA='cbs' AND table_name='mailbox' AND COLUMN_NAME='email_account')
 THEN
  alter table mailbox modify column email_account varchar(320);
 END IF;
 -- 如果不存在主键列，则设置双主键
 IF ((SELECT count(*) FROM information_schema.KEY_COLUMN_USAGE WHERE TABLE_SCHEMA ='cbs' AND table_name='mailbox' AND CONSTRAINT_NAME ='PRIMARY' AND (COLUMN_NAME ='email_account' OR COLUMN_NAME = 'company_id'))=0)THEN
    ALTER TABLE mailbox ADD primary key (company_id,email_account);
 -- 如果只存在一个主键列
 ELSEIF ((SELECT count(*) FROM information_schema.KEY_COLUMN_USAGE WHERE TABLE_SCHEMA ='cbs' AND table_name='mailbox' AND CONSTRAINT_NAME ='PRIMARY' AND (COLUMN_NAME ='email_account' OR COLUMN_NAME = 'company_id'))<2)THEN
    ALTER TABLE mailbox DROP PRIMARY KEY,ADD primary key (company_id,email_account);
 END IF;
  
END;
CALL mailbox_column_update();
DROP PROCEDURE IF EXISTS mailbox_column_update;

补充：mysql 修改主键自增,新增联合主键

ALTER TABLE `onduty_history`
MODIFY COLUMN `id` int(11) NOT NULL AUTO_INCREMENT FIRST ,
MODIFY COLUMN `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL AFTER `id`,
MODIFY COLUMN `onduty_date` datetime NOT NULL AFTER `name`,
ADD UNIQUE KEY (`id`),
ADD PRIMARY KEY (`name`, `onduty_date`);

以上为个人经验，希望能给大家一个参考，也希望大家多多支持免费资源网。如有错误或未考虑完全的地方，望不吝赐教。