确保下面的参数为空时候，where 后面有1=1的条件

不然会报错

因为第一个参数 带 and 了，参数为空的时候 where 条件 1=1  不报错

其实是为了方便正确拼接SQL

比如

SELECT * FROM TABLE WHERE 1=1 ${IF(LEN(控件1)==0,""," and 字段1='"+控件1+"'")} ${IF(LEN(控件2)==0,""," and 字段2='"+控件2+"'")}

它等效于

SELECT * FROM TABLE WHERE ${IF(LEN(控件1)==0,""," where 字段1='"+控件1+"'")} ${IF(LEN(控件2)==0,"",if(len(控件1)==0," where 字段2='"+控件2+"'"," and 字段2='"+控件2+"'"))}

第二种就明显容易拼接错误