alter table teacher add constraint pk_teacher primary key (t_id); select count(*) from teacher; 这个是oracle的测试和造数据脚本 create tablespace scott_data datafile '/home/oracle/oracle_space/sitpay1/scott_data.dbf' size 1024m autoextend on; create tablespace scott_index datafile '/home/oracl...
Another query is to describe the table that gets created. The image shown below illustrates the constraint that gets entered into the fields of thestudentPKtable. Drop Constraint From the MySQL Table Query to execute the DROP constraint in MySQL: ...
DELETE FROM：一旦执行此操作，表数据可以全部清除（不带WHERE）。同时，数据是可以实现回滚的。3.DDL和...
It looks like MySQL client that you use might simply not recognize the constraint type that is being dropped. So this might be both - problem with the version of your client libraries or with the Percona SQL Server not able to provide the constraint type to the client. ...
在MySQL中,我们可以通过以下语句查询数据库中所有的外键信息: SELECTTABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME,REFERENCED_TABLE_NAME,REFERENCED_COLUMN_NAMEFROMINFORMATION_SCHEMA.KEY_COLUMN_USAGEWHERETABLE_SCHEMA='your_database_name'ANDREFERENCED_TABLE_NAMEISNOTNULL; ...
mysql> truncate user; ERROR 1701 (42000): Cannot truncate a table referenced in a foreign key constraint (`test`.`account`, CONSTRAINT `fk_user_account` FOREIGN KEY (`uid`) REFERENCES `test`.`user` (`uid`)) 1. 2. 3. 报错的信息是,因为外键的约束,不能truncate这张表。
https://dev.mysql.com/doc/refman/8.0/en/create-table.html Good luck, Barry. Subject Written By Posted What's the general syntax to add constraint and drop constraint in the latest version of mysql? or does it vary according to constraint type(primary key, foreign key, check, not null et...
Assume we want to drop the UNIQUE constraint on the "Address" column, and the name of the constraint is "Con_First." To do this, we type in the following: MySQL: ALTER TABLE Customer DROP INDEX Con_First;Note that MySQL uses DROP INDEX for index-type constraints such as UNIQUE. ...
HASH 索引只支持等值比较,如“=”“IN()”或“<=>”。 HASH 索引不支持键的部分匹配,因为在计算 HASH 值的时候是通过整个索引值来计算的。 根据索引的具体用途,MySQL 中的索引在逻辑上分为以下 5 类: 1) 普通索引 普通索引是最基本的索引类型,唯一任务是加快对数据的访问速度,没有任何限制。创建普通索引时...
使用Oracle 兼容的表级外键约束控制,DISABLE 子表上的外键约束,则 TRUNCATE TABLE 父表可以成功;ENABLE 子表上的外键约束,则 TRUNCATE TABLE 失败,报错 ORA-00600: internal error code, arguments: -5594, Cannot truncate a table referenced in a foreign key constraint。 不管是否对子表外键约束 DISABLE,DROP ...