SQL Server查询效率问题，哪个高手可以帮忙解释下？

Question

下面5个SQL查询效率差异很多，BusinessIndex表中有300万条记录，
其中DatAuthor建立有索引，其它字段没有索引。
哪个高手可以分析下什么原因？ 非常感谢！
SELECT strCode, strIndex from BusinessIndex where 1=1 and UserOrgID=1 and ( BusinessIndex.strIndex like '%热水器%')

--查询4s

SELECT strAuthor, strIndex from BusinessIndex where 1=1 and UserOrgID=1 and ( BusinessIndex.strIndex like '%热水器%')

--查询4s

SELECT strCode,strAuthor, strIndex from BusinessIndex where 1=1 and UserOrgID=1 and ( BusinessIndex.strIndex like '%热水器%')

--查询39s

SELECT ROW_NUMBER() OVER (order by datAuthor Desc ) as hibernate_row_nr,
strCode, strAuthor,strIndex from BusinessIndex where 1=1 and UserOrgID=1 and ( BusinessIndex.strIndex like '%热水器%')
--查询4s

SELECT top 20 ROW_NUMBER() OVER (order by datAuthor Desc ) as hibernate_row_nr,
strCode, strAuthor,strIndex from BusinessIndex where 1=1 and UserOrgID=1 and ( BusinessIndex.strIndex like '%热水器%')
--查询40s