AI代码解释 ---约束演示---create tableyuser(id int primary key auto_increment comment'主键',namevarchar(10)notnullunique comment'姓名',age intcheck(age>0&&age<=120)comment'年龄',statuschar(1)default'1'comment'状态',genderchar(1)comment'性别')comment'用户表';--插入数据 insert intoyuser(n...
CREATE TABLE [IF NOT EXISTS] table_name( column_definition1, column_definition2, …….., table_constraints ); 也可简写为: CREATE TABLE table_name (column_name column_type); 上述语法的参数说明如下: 以下例子中我们将在 RUNOON 数据库中创建数据...
Like shown here, you have add every constraint as if clause to your trigger., because mysql 5.x doesn't supportCHECKconstraints Also note thatOrderis areserved word, and you shouldn't use them in table or column names else you have always to use Backticks in every Query CREATETABLEIFNOT...
If set to 1 (the default), foreign key constraints for InnoDB tables are checked. If set to 0, foreign key constraints are ignored, with a couple of exceptions. When re-creating a table that was dropped, an error is returned if the table definition does not conform to the foreign key ...
column_name_2 column_type_2 constraints , ……) column_name 是列的名字 column_type 是列的数据类型 contraints 是这个列的约束条件 1.1.1、创建一张简单的表 mysql>createtableorders (ordernamevarchar(10),createtime date,ordermoneydecimal(10,2),ordernumberint(2)); ...
Foreign key constraints can be added later using ALTER TABLE. You can precede the SELECT by IGNORE or REPLACE to indicate how to handle rows that duplicate unique key values. With IGNORE, rows that duplicate an existing row on a unique key value are discarded. With REPLACE, new rows ...
MySQL has no limit on the number of tables. The underlying file systemmay have a limit on the number of files that represent tables.Individual storage engines may impose engine-specific constraints.InnoDB permits up to 4 billion tables.For information about the physical representation of a table,...
create_ definition: column_definition: data_type index_col_name: index_type: index_option: reference_definition: table_options: Limits on MySQL table size The maximum table size for MySQL databases is determined by operating system constraints on file sizes, not by MySQL internal limits. The foll...
mysql每新建一个连接,就会自动生成一些库,其中一个库叫做information_schema,这个库里有张表叫做table_constraints。这张表记录了连接里的所有约束信息。比如是否是主键约束,外键约束,唯一性约束,约束名,表名等信息。还有张表叫key_column_usage,他记录了每个表字段的信息,包括了这个字段是否是外键,对应那张表的主键。也...
SELECT * FROM information_schema.TABLE_CONSTRAINTS WHERE table_name='emp'; #删除外键约束 ALTER TABLE emp DROP FOREIGN KEY fk_emp_deptno; #查看指定表的索引 SHOW INDEX FROM emp; #最后手动删除索引 ALTER TABLE emp DROP INDEX fk_emp_deptno; ...