mysql判断表中字段或者索引是否存在，如果不存在则创建

DROP PROCEDURE IF EXISTS schema_change;  
DELIMITER //
CREATE PROCEDURE schema_change() BEGIN 
DECLARE  CurrentDatabase VARCHAR(100);
SELECT DATABASE() INTO CurrentDatabase;
IF NOT EXISTS (SELECT * FROM information_schema.statistics WHERE table_schema=CurrentDatabase AND table_name = "rtc_phototype" AND index_name = "index_name") THEN  
   ALTER TABLE `rtc_Phototype` ADD INDEX index_name ( `imgtype` );
END IF;  
END//  
DELIMITER ;  
CALL schema_change();

判断索引是否存在：

DROP PROCEDURE IF EXISTS schema_change;  
DELIMITER //
CREATE PROCEDURE schema_change() BEGIN 
DECLARE  CurrentDatabase VARCHAR(100);
SELECT DATABASE() INTO CurrentDatabase;
IF NOT EXISTS (SELECT * FROM information_schema.statistics WHERE table_schema=CurrentDatabase AND table_name = "rtc_phototype" AND index_name = "index_name") THEN  
   ALTER TABLE `rtc_Phototype` ADD INDEX index_name ( `imgtype` );
END IF;  
END//  
DELIMITER ;  
CALL schema_change();