在MySQL中显示对表命令的约束？
您可以借助SHOW命令在表上显示约束。语法如下-
show create table yourTableName;
上面的命令将显示表ENGINE的所有约束。使用此功能，您甚至可以查看所有列名和相应的数据类型。
要了解上述MySQL语句，让我们首先创建一个表-
mysql> create table ShowConstraintsDemo -> ( -> BookId int not null, -> BookName varchar(200) not null, -> BookAuthor varchar(200) Unique not null, -> Primary key(BookId,BookName) -> );
现在，您可以应用上述语法以显示对表的约束。查询如下-
mysql> show create table ShowConstraintsDemo;
以下是显示所有约束的输出-
+---------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Table | Create Table | +---------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | ShowConstraintsDemo | CREATE TABLE `showconstraintsdemo` ( `BookId` int(11) NOT NULL, `BookName` varchar(200) COLLATE utf8mb4_unicode_ci NOT NULL, `BookAuthor` varchar(200) COLLATE utf8mb4_unicode_ci NOT NULL, PRIMARY KEY (`BookId`,`BookName`), UNIQUE KEY `BookAuthor` (`BookAuthor`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci | +---------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.05 sec)
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