ALTER TABLE table_name 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...
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 table_name DROP CONSTRAINT MyPrimaryKey; 如果是 MYSQL ,代码是这样: ALTER TABLE table_name DROP PRIMARY KEY...
JOIN pg_attribute a ON a.attrelid = i.indrelid AND a.attnum = ANY (i.indkey) WHERE i.indrelid = 'your_table_name'::regclass; your_table_name需要替换为你要操作的数据表名。 2、删除主键 确认主键信息后,可以使用以下SQL语句删除主键: ALTER TABLE your_table_name DROP CONSTRAINT your_prima...
ALTER TABLE table_name DROP INDEXMyUniqueConstraint; DROP PRIMARY KEY (删除主键),语法如下: ALTER TABLE table_name DROP CONSTRAINTMyPrimaryKey; 如果是 MYSQL ,代码是这样: ALTER TABLE table_name DROP PRIMARY KEY;
删除已存在的外键约束。 添加一个 ON DELETE CASCADE 的外键约束。 删除外键约束 格式: alter table 从表名 drop constraint 从表的外键约束名; 1 参考文档 postgres.cn/docs/12/ddl-constraints.html#DDL-CONSTRAINTS-FK postgresql
ALTER TABLE tb_dept1 DROP managerid; 【例2】删除数据表tb_emp9中的外键约束。首先创建表tb_emp9,创建外键deptId关联tb_dept1表的主键id,SQL语句如下:CREATE TABLE tb_emp9 ( id INT PRIMARY KEY, name VARCHAR(25), deptId INT, salary FLOAT, CONSTRAINT fk_emp_dept FOREIGN KEY (deptId) ...
test=#altertabletbl_primaryaddconstraintpk_tbl_primary_a_bprimarykey(a,b);ALTERTABLE 方式二 将重复数据全部删除 第一步:删除主键约束,清空表,写入测试数据 altertabletbl_primarydropconstraintpk_tbl_primary_a_b ;ALTERTABLEtest=#deletefromtbl_primary;DELETE8test=#insertintotbl_primary (a,b)values(1...
= 'PRIMARY': # 如果不是主键外键，才删除外键并迁移数据到新表 cur.execute(f"ALTER TABLE {table} DROP CONSTRAINT {fk[]};") data = data.join(data.loc[:, fk[1]:], on=fk[], how='left') # 删除外键后，使用left join将数据迁移到新表 data = data.rename({fk[1]: f"{table...
Indexes:"locations_pkey" PRIMARY KEY, btree (location_id, country_id) Now execute the following statement. Sample Solution: Code: ALTERTABLElocationsDROPCONSTRAINTlocations_pkey; Copy Output: Now see the structure of the table locations after alteration. ...
= 'PRIMARY': # 如果不是主键外键,才删除外键并迁移数据到新表 cur.execute(f"ALTER TABLE {table} DROP CONSTRAINT {fk[0]};") data = data.join(data.loc[:, fk[1]:], on=fk[0], how='left') # 删除外键后,使用left join将数据迁移到新表 data = data.rename({fk[1]: f"{table}_new_...