在MySQL中选择单行？
如果要基于主键选择单个行，请使用WHERE子句。语法如下-
SELECT * FROM yourTableName WHERE yourPrimaryKeyColumnName = someValue;
为了理解上述语法，让我们创建一个表。创建表的查询如下-
mysql> create table selectWithPrimaryKey -> ( -> Id int NOT NULL AUTO_INCREMENT, -> Name varchar(20), -> Age int, -> Marks int, -> PRIMARY KEY(Id) -> );
使用insert命令在表中插入一些记录。查询如下-
mysql> insert into selectWithPrimaryKey(Name,Age,Marks) values('Larry',24,98);
mysql> insert into selectWithPrimaryKey(Name,Age,Marks) values('John',23,89);
mysql> insert into selectWithPrimaryKey(Name,Age,Marks) values('Mike',21,85);
mysql> insert into selectWithPrimaryKey(Name,Age,Marks) values('Sam',26,56);
mysql> insert into selectWithPrimaryKey(Name,Age,Marks) values('Carol',21,59);
mysql> insert into selectWithPrimaryKey(Name,Age,Marks) values('Bob',20,91);
mysql> insert into selectWithPrimaryKey(Name,Age,Marks) values('David',28,93);使用select语句显示表中的所有记录。查询如下-
mysql> select *from selectWithPrimaryKey;
以下是输出-
+----+-------+------+-------+ | Id | Name | Age | Marks | +----+-------+------+-------+ | 1 | Larry | 24 | 98 | | 2 | John | 23 | 89 | | 3 | Mike | 21 | 85 | | 4 | Sam | 26 | 56 | | 5 | Carol | 21 | 59 | | 6 | Bob | 20 | 91 | | 7 | David | 28 | 93 | +----+-------+------+-------+ 7 rows in set (0.00 sec)
以下是从表中选择一行的查询-
mysql> select *from selectWithPrimaryKey where Id = 6;
这是输出-
+----+------+------+-------+ | Id | Name | Age | Marks | +----+------+------+-------+ | 6 | Bob | 20 | 91 | +----+------+------+-------+ 1 row in set (0.00 sec)