1,添加联合主键: ALTER TABLE 表名 ADD CONSTRAINT 联合主键名称 PRIMARY KEY (列名1, 列名2); 1. 2. 2,如果存在先删除,执行删除sql,删除原来的主键 如果创建的时候报错multiple primary keys for table “student_info” are not allowed, 那就要先删除原来的表中的主键 ALTER TABLE 表名 DROP CONSTRAINT 联...
Sql - Referencing multiple primary keys in another table, create table TEST_TABLE2 /* */ ( PRIMARY_COLUMN1 int references TEST_TABLE1 (PRIMARY_COLUMN1) not null, primary key (PRIMARY_COLUMN1) ); What you have here is one primary key that happens to contain multiple columns (aka. "compo...
您可以随时在SQLServer management studio中可视化地设计您的表（包括关系），然后让它为它们编写脚本并查看...
CREATE TABLE `user_1` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT '主键', `email` varchar(32) NOT NULL DEFAULT '' COMMENT '邮箱', `name` varchar(11) DEFAULT '' COMMENT '名字', PRIMARY KEY (`id`), UNIQUE KEY `uk-email` (`email`) ) ENGINE=InnoDB DEFAULT CHARSET=ut...
id INT PRIMARY KEY, column1 VARCHAR(50) ); -- Unique Key CREATE TABLE example_table ( id INT UNIQUE, column1 VARCHAR(50) ); Auto-increment Primary Key in SQL: Description:An Auto-increment Primary Key is a numeric value that automatically increments. Commonly used for surrogate keys. ...
then adding another one is a hard mistake. A table itself does not contain info on how was it created. You have a got a workaround that is very easy to implement, since "DROP PRIMARY KEY" is a very simple command. MySQL can not do "silent" dropping of any keys, since that would ...
referenced column or columns in the referenced table. FOREIGN KEY constraints can reference only columns that are PRIMARY KEY or UNIQUE constraints in the referenced table or columns referenced in a UNIQUE INDEX on the referenced table. Foreign keys on computed columns must also be marked PERSISTED...
SQL 複製 CREATE TABLE TestBatch (ColA INT PRIMARY KEY, ColB CHAR(3)); GO INSERT INTO TestBatch VALUES (1, 'aaa'); INSERT INTO TestBatch VALUES (2, 'bbb'); INSERT INTO TestBatch VALUSE (3, 'ccc'); -- Syntax error. GO SELECT * FROM TestBatch; -- Returns no rows....
When you partition a non-unique, clustered index, the Database Engine by default adds the partitioning column to the list of clustered index keys, if it is not already specified. When partitioning a non-unique, nonclustered index, the Database Engine adds the partitioning column as a non-key...
Creates a foreign (non-primary) index, specifies the index key expression, and establishes a relationship to a parent table. You can create multiple foreign indexes for the table, but foreign index expressions must specify different fields in the table. The TagName4 parameter specifies the name ...