Summary: in this tutorial, you will learn about MySQL foreign key and how to create, add, and drop foreign key constraints in MySQL. Introduction to MySQL foreign key# A foreign key is a field in a table that matches another field of another table. A foreign key places constraints on ...
可以使用alert table或create index语给数据表加索引。mysql内部会把create index语句映射为alter table 操作。 alert table tab1_name add INDEX index_name alert table tab1_name add UNIQUE index_name alert table tab1_name add PRIMARY KEY (index_name) alert table tab1_name add FullTEXT index_name ...
26 PRIMARY KEY (`id`) 27 ) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8; 28 29 ALTER TABLE files ADD CONSTRAINT files_users_fk FOREIGN KEY(`user_id`) REFERENCES users(`id`); 可以看出 files 依赖表users ,依赖表不能先删除。也就是说,需要先删除当前表,再删除外键关联表 我们来看看概...
Setting foreign_key_checks to 1 does not trigger a scan of the existing table data. Therefore, rows added to the table while foreign_key_checks=0 will not be verified for consistency. 1. 2. 3. 4. 5. 当FOREIGN_KEY_CHECKS设置为0时,外键约束会被忽略,而当FOREIGN_KEY_CHECKS设置为1时不会...
Assigned to:CPU Architecture:Any [12 Oct 2017 19:42] Bradley Grainger Description:When lower_case_table_names=1, an automatically-generated constraint name that conflicts (case insensitively) with an existing constraint name will cause an "ALTER TABLE ADD FOREIGN KEY" statement to fail with the...
I am creating two tables then doing an alter table to add a foreign key constraint and it gives the following error: Error Code: 1005. Can't create table 'mydb.#sql-870_16' (errno: 150) Here is a simple test to prove it:
B. CREATE TABLE C. DROP TABLE D. RENAME TABLE 答案:A 7. MySQL中,哪个命令用于删除数据库中的表? A. DROP TABLE B. REMOVE TABLE C. DELETE TABLE D. CLEAR TABLE 答案:A 8.在MySQL中,哪个命令用于重命名表? A. RENAME TABLE B. CHANGE TABLE C. ALTER TABLE D. UPDATE TABLE 答案:A 9. MyS...
alter table 表名称 修改选项;修改选项的语法格式如下所示。add column 列名称 类型; change column 旧...
Bug #70171ALTER TABLE add foreign key causes failure to rename temporary table on 5.6.12+ Submitted:28 Aug 2013 3:59Modified:12 Nov 2013 8:43 Reporter:Andrew MannEmail Updates: Status:DuplicateImpact on me: None Category:MySQL Server: InnoDB storage engineSeverity:S2 (Serious) ...
drop table if exists tb_role_acl;检查表是否存在，如果存在则删除表，估计你之前已经创建过该表，然后其中涉及到外键，这种情况首先得删除外键约束，然后才能删除表。删除约束的语法如下：alter table 表名称 drop constraint 约束名称