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...
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...
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 ...
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; 这些命令使数据库管理员能够灵活地管理和...
@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...
{ 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 | ...
[ 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: { ...
If a column has the PRIMARY KEY, UNIQUE KEY, KEY, or FULLTEXT constraint, you can change the column to a NOT NULL column by executing the CHANGE/MODIFY COLUMN statement with a COMMENT clause. However, if you change the column to a NULLABLE column in this case, an error is returned. ...
CREATE[TEMPORARY|TEMP]TABLEtable(columntype[NULL|NOTNULL][UNIQUE][DEFAULTvalue][column_constraint_clause|PRIMARYKEY}[...]][,...][,PRIMARYKEY(column[,.][,CHECK(condition)][,table_constraint_clause])[INHERITS(inherited_table[,...])]TEMPORARY此表只是为这次会话创建,并且在会话结束后自动删除。当临...
ERROR: duplicate key value violates unique constraint "unique_url" DETAIL: Key (url)=(https://neon.tech/postgresql/) already exists. The following statement changes the name of the links table to urls: ALTER TABLE links RENAME TO urls; In this tutorial, you have learned how to use the P...