日日操夜夜添-日日操影院-日日草夜夜操-日日干干-精品一区二区三区波多野结衣-精品一区二区三区高清免费不卡

以下是語(yǔ)法 –

alter table yourSecondTableName
add constraint `yourConstraintName`
foreign key(`yourSecondTableNamePrimaryKey`)
references yourFirstTableName(yourFirstTablePrimaryKeyColumnName);

登錄后復(fù)制

為了理解上述語(yǔ)法，讓我們首先創(chuàng)建一個(gè)表 –

mysql> create table demo65
−> (
−> id int not null primary key,
−> name varchar(20)
−> );
Query OK, 0 rows affected (0.57 sec)

登錄后復(fù)制

以下是創(chuàng)建第二個(gè)表的查詢(xún) –

mysql> create table demo66
−> (
−> user_id int not null primary key,
−> address varchar(200)
−> );
Query OK, 0 rows affected (1.80 sec)

登錄后復(fù)制

以下是將主鍵引用為外鍵的查詢(xún) –

mysql> alter table demo66
−> add constraint `id_fk`
−> foreign key(`user_id`)
−> references demo65(id);
Query OK, 0 rows affected (3.76 sec)
Records: 0 Duplicates: 0 Warnings: 0

登錄后復(fù)制

讓我們使用 SHOW CREATE TABLE 命令檢查表的整體描述。以下是查詢(xún) –

mysql> show create table demo66;

登錄后復(fù)制

這將產(chǎn)生以下輸出 –

+--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table +--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| demo66 | CREATE TABLE `demo66` (
`user_id` int NOT NULL,
`address` varchar(200) DEFAULT NULL,
PRIMARY KEY (`user_id`),
CONSTRAINT `id_fk` FOREIGN KEY (`user_id`) REFERENCES `demo65` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |
+--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

登錄后復(fù)制

以上就是如何將主鍵作為外部引用到MySQL中的各種表？的詳細(xì)內(nèi)容，更多請(qǐng)關(guān)注www.92cms.cn其它相關(guān)文章！