Write a SQL query to create a table with three columns: id, name, and age. Add a primary key constraint on the id column. Write a SQL query to create a table with four columns: product_id, product_name, price,
可使用 INSERT INTO 语句向空表写入数据。 SQL 约束 约束用于限制加入表的数据的类型。 可以在创建表时规定约束(通过 CREATE TABLE 语句),或者在表创建之后也可以(通过 ALTER TABLE 语句)。 我们将主要探讨以下几种约束: NOT NULL UNIQUE PRIMARY KEY FOREIGN KEY CHECK DEFAULT SQL NOT NULL 约束 NOT NULL 约束...
{INCLUDING|EXCLUDING} {DEFAULTS|CONSTRAINTS|INDEXES|STORAGE|COMMENTS|PARTITION|RELOPTIONS|DISTRIBUTION|DROPCOLUMNS|ALL} 其中索引参数index_parameters为: [ WITH ( {storage_parameter = value} [, ... ]) ] 参数说明 UNLOGGED 如果指定此关键字,则创建的表为非日志表。在非日志表中写入的数据不会被写入到预...
In this SQL tutorial, we will look at a common task of creating a database table. We will look at some do’s and don’ts while creating a simple table as well as adding constraints and schemas. We will also explain the steps that are required in the create table operation, what each...
约束检查的时间可以用SET CONSTRAINTS命令修改。 表5-191 WITH参数说明(存储相关) 参数 描述 取值范围 ORIENTATION 指定表数据的存储方式,即行存方式、列存方式,该参数设置成功后就不再支持修改。 取值范围: ROW,表示表的数据将以行式存储。 行存储适合于OLTP业务,此类型的表上交互事务比较多,一次交互会涉及表中...
查看information_schema.TABLE_CONSTRAINTS视图 查看information_schema.CHECK_CONSTRAINTS视图 constraint_name约束名称,最多包含 64 个字符。 约束名称的开头结尾中间都允许有空格,但需要用"`"标识名称的开头和结尾。 约束名称可以包含特殊字符"$"。 如果约束名称为保留字,需要用"`"标识,否则会报错。
DEFERRABLE:可以推迟到事务结尾使用SET CONSTRAINTS命令检查。 NOT DEFERRABLE:在每条命令之后马上检查。 INITIALLY IMMEDIATE:那么每条语句之后就立即检查它。 INITIALLY DEFERRED:只有在事务结尾才检查它。 - WITH ( {storage_parameter = value} [, ... ] ) 为表或索引指定一个可选的存储参数。 - COMPRESS|NOCOMPRE...
If the name of a history table is specified during history table creation, you must specify the schema and table name. If the history table doesn't exist, the system generates a new history table matching the schema of the current table in the same filegroup as the current table, creating...
If the name of a history table is specified during history table creation, you must specify the schema and table name. If the history table doesn't exist, the system generates a new history table matching the schema of the current table in the same filegroup as the current table, creating...
[ WITH ( <table_option> [ ,...n ] ) ] [ ; ] <column_definition> ::= column_name <data_type> [ FILESTREAM ] [ COLLATE collation_name ] [ NULL | NOT NULL ] [ [ CONSTRAINT constraint_name ] DEFAULT constant_expression ] | [ IDENTITY [ ( seed ,increment ) ] [ NOT FOR ...