ALTERTABLEtable_nameDROPINDEXMyUniqueConstraint; DROP PRIMARY KEY (删除主键),语法如下: ALTERTABLEtable_nameDROPCONSTRAINTMyPrimaryKey; 如果是 MYSQL ,代码是这样: ALTERTABLEtable_nameDROPPRIMARYKEY; TRUNCATE TABLE PostgreSQL 中 TRUNCATE TABLE 用于删除表的数据,但不删除表结构。 也可以用 DROP TABLE 删除表...
ALTER TABLE table_name ADD CONSTRAINTMyPrimaryKeyPRIMARY KEY(column1,column2...); DROP CONSTRAINT (删除约束),语法如下: ALTER TABLE table_name DROP CONSTRAINTMyUniqueConstraint; 如果是 MYSQL ,代码是这样: ALTER TABLE table_name DROP INDEXMyUniqueConstraint; DROP PRIMARY KEY (删除主键),语法如下: A...
ADD CONSTRAINT MyPrimaryKey PRIMARY KEY (column1, column2...); DROP CONSTRAINT (删除约束),语法如下: ALTER TABLE table_name DROP CONSTRAINT MyUniqueConstraint; 如果是 MYSQL ,代码是这样: ALTER TABLE table_name DROP INDEX MyUniqueConstraint; DROP PRIMARY KEY (删除主键),语法如下: ALTER TABLE tabl...
ALTER TABLE table_name ADD CONSTRAINT MyUniqueConstraint CHECK (CONDITION); The basic syntax of ALTER TABLE to ADD PRIMARY KEY constraint to a table is as follows −ALTER TABLE table_name ADD CONSTRAINT MyPrimaryKey PRIMARY KEY (column1, column2...); ...
ADD CONSTRAINT constraint_name constraint_type (column_name); ALTER TABLE table_name ENABLE/DISABLE TRIGGER trigger_name; 在PostgreSQL中,ALTER命令也提供了类似的功能,并且还允许重命名列: ALTER TABLE table_name RENAME COLUMN old_column_name TO new_column_name; ...
ALTER TABLE table_name DROP CONSTRAINT constraint_name; 需要注意的是,在使用ALTER TABLE命令时,需要谨慎操作,以免对数据造成损失。建议在进行修改操作之前,先备份数据,并在测试环境中进行验证。 推荐的腾讯云相关产品: 腾讯云数据库:提供了MySQL、PostgreSQL、MongoDB等多种数据库产品,支持自动备份、监控告警等功能。
ADD CONSTRAINT PostgreSQL ALTER TABLE example Let us consider the tablesorders. SQL Code: CREATE TABLE orders( ord_no integer PRIMARY KEY, ord_date date NOT NULL, cus_name character(25) NOT NULL, item_code integer NOT NULL, item_grade character(1)NOT NULL DEFAULT 'A', vendor_code numeric...
{ new_owner | CURRENT_USER | SESSION_USER } REPLICA IDENTITY { DEFAULT | USING INDEX index_name | FULL | NOTHING} 并且table_constraint_using_index 是: [ CONSTRAINT constraint_name ] { UNIQUE | PRIMARY KEY } USING INDEX index_name [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | ...
您所描述的是使用ON DELETE CASCADE选项的教科书外键约束。在SQL中，您可以在场景中创建表grapes时隐式...
PrimaryKeyConstraint('role_focus_user_id') ) with op.batch_alter_table('role', schema=None) as batch_op: batch_op.add_column(sa.Column('duration', sa.Integer(), nullable=True)) batch_op.add_column(sa.Column('role_type', sa.Enum('leadlink', 'elected', 'assigned'), nullable=True...