@level0name=N'dbo', @level1type=N'TABLE',@level1name=N'表名', @level2type=N'COLUMN',@level2name=N'列名'; exec sys.sp_addextendedproperty @name=N'MS_Description', @value=N'列说明' , @level0type=N'SCHEMA', @level0name=N'dbo', @level1type=N'TABLE',@level1name=N'表名', @...
alter TABLE my_pri MODIFY number char(11) PRIMARY KEY; 1. 第二种方式示例如下: --增加单一主键 alter table table_name add primary key(column) ; alter TABLE my_pri add PRIMARY KEY(number,course); --增加复合主键 alter table my_pri add CONSTRAINT pk_score PRIMARY KEY(score) --使用关键字C...
ADD COLUMN vdr_id int not null AFTER cat_id; To add a foreign key to the products table, you use the following statement: 1 2 3 4 5 ALTER TABLE products ADD FOREIGN KEY fk_vendor(vdr_id) REFERENCES vendors(vdr_id) ON DELETE NO ACTION ON UPDATE CASCADE; Now, the products table ...
MySQL添加外键报错 - referencing column 'xx' and referenced column 'xx' in foreign key constraint 'xx' are incompatible MySQL给两个表添加外键时,报错 翻译意思是:外键约束“xx”中的引用列“xx”和引用列“xx”不兼容 说明两个表关联的列数据类型不一致,比如:varchar 与 int,或者 int无符号 与 int有符...
MySQL supports foreign keys, which permit cross-referencing related data across tables, and foreign key constraints, which help keep the related data consistent. A foreign key relationship involves a parent table that holds the initial column values, and a child table with column values that refer...
But when not using NOT NULL on creation on Column is works fine to add a foreign key ??? Can someone please explain this to me ? because I have created a column with the not null option and added a foreign key before and then i worked.. so where am i going wrong ?Navigate...
NDB Cluster stores foreign key names using the same lettercase with which they are created. Table and column identifiers in aFOREIGN KEY ... REFERENCESclause can be quoted within backticks (`). Alternatively, double quotation marks (") can be used if theANSI_QUOTESSQL mode is enabled. The...
To prevent MySQL error 1215, you must ensure that the column is set to the default null value. Conclusion This article has explained the reason for MySQL’s “#1215 – Cannot Add Foreign Key Constraint” error, how to find the cause, and how to fix it with four effective methods. ...
SELECT * FROM t1 WHERE column1=(SELECT column1 FROM t2); 根据子查询结果不同,分为:标量子查询(子查询结果为单个值)、列子查询(子查询结果为一列)、行子查询(子查询结果为一行)、表子查询(子查询结果为多行多列) 根据子查询位置,分为:WHERE之后、FROM之后、SELECT之后。 代码语言:sql AI代码解释 #标量...
Missing column references in the references clauses ... foreign key (ptr_num) references painter(ptr_num) on update cascade, foreign key (gal_num) references gallery(gal_num) on update cascade Also, a primary key is by definition unique; it's redundant, and therefore a mistake, to define...