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...
给表ADD PRIMARY KEY(添加主键),语法如下: 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 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...
DROP CONSTRAINT item_vendor_ukey; Add PRIMARY KEY constraint If we want to add a primary key constraint inorderstable the following SQL can be used. Only one primary key is allowed for a table. So, we have to assume that we have no pre-defined primary key in the table which we are ...
@文心快码postgresql alter table add constraint 文心快码 在PostgreSQL中,ALTER TABLE语句用于修改现有表的结构,例如添加或删除列、添加或删除约束等。下面是对你问题的详细回答: ALTER TABLE语句的用途: ALTER TABLE语句在PostgreSQL中用于修改已存在的表的结构。这包括添加或删除列、修改列的数据类型、添加或删除约束...
语法：ALTER TABLE table_name ADD PRIMARY KEY ;功能：为表添加一个主键，确保主键列中的值唯一。删除约束：语法：ALTER TABLE table_name DROP CONSTRAINT constraint_name;功能：从表中删除指定的约束。注意：在 PostgreSQL 中，删除主键的语法与添加主键不同，但并未在提供的参考信息中明确给出具体的...
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; ...
The below snippet will let you understand how to add the“PRIMARY KEY”constraint in“PostgreSQL”using the“ALTER TABLE”command: ALTER TABLE team_info ADD PRIMARY KEY (team_rating); The output verified that multiple primary keys in the table“team_info”are not allowed. This is how you can...
[ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] UNIQUE、PRIMARY KEY以及EXCLUDE约束中的index_parameters是: [ INCLUDE ( column_name [, ... ] ) ] [ WITH ( storage_parameter [= value] [, ... ] ) ] [ USING INDEX TABLESPACE tablespace_name ] exclude_element in an EXCLUDE constraint is: { ...
ERROR: duplicatekeyvalueviolatesuniqueconstraint"unique_url"DETAIL:Key(url)=(https://neon.tech/postgresql/) alreadyexists. The following statement changes the name of thelinkstable tourls: ALTERTABLElinksRENAMETOurls; In this tutorial, you have learned how to use the PostgreSQLALTER TABLEstatement ...