这句SQL是什么意思呢?

[bestpcboy]

select id,name,descr='  '+SUBSTRING(description,0,100)+'...',image = case when(not cover is null) then<img src = ReadBookCover.aspx?id='+cast(id as varchar(10))+'Border = 1 width = 70 height =100>' else'<img src = img/pic.jpg border = 1 width = 70 height = 100>' end from book order gy hits DESC"

帮助解释一下这句:
image = case when(not cover is null) then<img src = ReadBookCover.aspx?id='+cast(id as varchar(10))+'Border = 1 width = 70 height =100>'

[fengfangfang]

image = case when(not cover is null) then '<img src = ReadBookCover.aspx?id='+cast(id as varchar(10))+'Border = 1 width = 70 height =100>'

判断cover是否为null,如果不为null,则输出一段html代码，并将id作为参数.

[贝贝壳壳]

如果　cover不为null，则image='<img src ....

[chxljtt]

一个CASE的分支选则，当(not cover is null)为真则跳转到ReadBookCover.aspx?id='+cast(id as varchar(10))这个页面！后面是对页面设置！

[kellyrong]

case when是條件,then是結果

[lovefootball]

楼上说的很全面了