schema([node()]) end. 2. 判断表是否存在 case lists:member(agent_cache_table, mn...
drop table Student ---创建subject课程表--- 代码如下: ---1、判断表是否存在;若存在则删除再创建,若不存在则直接创建--- if exists(select * from sysobjects where name = 'subject') drop table subject use School go ---创建subject课程表-- create table subject ( SubjectNo int not null identity...
alter table 表名 add constraint 检查约束名(规范"ck_"开头) check(表达式); 添加默认值约束 alter table 表名 add constraint 默认值约束名(规范"df_"开头) default('默认值') for 列名 添加主外键约束: alter table 表名(外键表) add constraint 外键约束名(规范"fk_"开头) foreign key(外键名) referen...
...以下使用一段SQL代码进行演示: USE PersonInfo --使用PersonInfo数据库 GO IF EXISTS (SELECT * FROM sys.tables WHERE [name...约束条件为检查约束的列Identity ) GO CREATE TABLE Employee --创建Employee(雇员)表 ( --索引 EmployeeID int IDENTITY...
SqlAlchemy already supports these operations on DropTable and CreateTable so this would essentially be a pass-through in a similar manner. Databases / Backends / Drivers targeted Postgresql Example Use Much like drop_index, I'd expect op.drop_table('foobar', if_exists=True) to produce DROP ...
Table的一般使用 mytable=Table("mytable", metadata, Column('mytable_id',Integer, primary_key=True), Column('value', String(50)) ) Table的参数: name表名称 metadata该表所属的MetaData对象 其他参数: 通过Column指定一列数据, 格式见:Column定义 ...
if not os.path.exists(SQLALCHEMY_MIGRATE_REPO): api.create(SQLALCHEMY_MIGRATE_REPO,‘database repository‘) api.version_control(SQLALCHEMY_DATABASE_URI,SQLALCHEMY_MIGRATE_REPO)else: api.version_control(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO, api.version(SQLALCHEMY_MIGRATE_REPO)) step ...
Added support for :paramref:`.Operations.create_table.if_not_exists` and :paramref:`.Operations.drop_table.if_exists`, adding similar functionality to render IF [NOT] EXISTS for table operations in a similar way as with indexes. Pull request courtesy Aaron Griffin. Fixes: #1520 Closes: #1521...
(Base): __tablename__ = "c" id = Column(Integer, primary_key=True) b_id = Column(ForeignKey("b.id")) value = Column(String) class AtoB(Base): __tablename__ = "atob" a_id = Column(ForeignKey("a.id"), primary_key=True) b_id = Column(ForeignKey("b.id"), primary_key=...
sqlalchemy.exc.InternalError: (pymysql.err.InternalError) (1091, "Can't DROP 'users_ibfk_1'; check that column/key exists") [SQL: ALTER TABLE users DROP FOREIGN KEY users_ibfk_1] 解决办法: 将每个数据库表类型InnoDB转为 MyISAM 如果报错ERROR 1217 (23000): Cannot delete or update a parent...