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法律如何判断 MySQL 中的一列是否为主键？
若要判断一列是否为主键，请使用 COLUMN_NAME 和 COLUMN_KEY='PRI'。语法如下所示 −
select column_name, case when column_key= 'PRI' then 'yourMessage1' else ''yourMessage2' end as anyAliasName from information_schema.columns where table_schema =database() and `table_name` = yourTableName order by `table_name`, ordinal_position;
要了解上述语法，我们创建一个表 −
mysql> create table DemoTable1886 ( Id int NOT NULL, FirstName varchar(20), LastName varchar(20), Age int, DateOfBirth datetime, Education varchar(40), PRIMARY KEY(Id) ); Query OK, 0 rows affected (0.00 sec)
以下是查询特定列是否为主键的方法 −
mysql> select column_name, case when column_key= 'PRI' then 'This is a Primary key Column' else 'This is not a Primary key Column' end as Output from information_schema.columns where table_schema =database() and `table_name` = 'DemoTable1886' order by `table_name`, ordinal_position;
这将生成以下输出 −
+-------------+--------------------------------+ | COLUMN_NAME | Output | +-------------+--------------------------------+ | Id | This is a Primary key Column | | FirstName |This is not a Primary key Column| | LastName |This is not a Primary key Column| | Age |This is not a Primary key Column| | DateOfBirth |This is not a Primary key Column| | Education |This is not a Primary key Column| +-------------+--------------------------------+ 6 rows in set (0.00 sec)
更新于:2019-12-27
356 次阅读
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