在MySQL准备语句中使用变量
让我们首先创建一个表-
mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(20), LastName varchar(20) );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable(FirstName,LastName) values('John','Smith');
mysql> insert into DemoTable(FirstName,LastName) values('David','Miller');
mysql> insert into DemoTable(FirstName,LastName) values('John','Doe');
mysql> insert into DemoTable(FirstName,LastName) values('Chris','Brown');使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
这将产生以下输出-
+----+-----------+----------+ | Id | FirstName | LastName | +----+-----------+----------+ | 1 | John | Smith | | 2 | David | Miller | | 3 | John | Doe | | 4 | Chris | Brown | +----+-----------+----------+ 4 rows in set (0.00 sec)
以下是在MySQL中使用prepare语句时设置变量的查询-
mysql> set @yourTableName :='DemoTable';
mysql> set @query :=CONCAT('select `LastName` from ',@yourTableName, ' where Id=3 ');
mysql> prepare myStatement from @query;
Statement prepared
mysql> execute myStatement;这将产生以下输出-
+----------+ | LastName | +----------+ | Doe | +----------+ 1 row in set (0.00 sec)