在选择查询中用变量替换字段名称

Question

我想用变量替换字段名称以从PHP和MySQL中的表中获取数据.

select * from demo where variable-1

代替 select * from demo where fieldname=1

因为从drowpdown中选择了50多个fieldname.

Answer 1

变量将无法正常工作的field names,以及table Names.它唯一能做的就是当你创建动态sql时,例如

SET @variableName = 'fieldname';
SET @sql = CONCAT('SELECT * FROM demo WHERE `', @variableName, '` = 1');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

• 动态SQL(准备语句)