利用count(case when ··· then ··· end ) 可以统计不同状态的物品数量

  select  d.tools_name, null as sum,null as num,dtp.specs,dtp.type,count( case when state =0 then 'state' end ) as 在库 ,
count(case when state =1 then 'state' end) 借出 ,
count(case when state =2 then 'state' end)  丢失,
count(case when state =3 then 'state' end)  报废
 from  dm_tools_KC   d  left join dm_tools_project dtp on d.tools_name = dtp.tools_name  where    d.TOOLS_NAME ='BH' group by d.tools_name,dtp.specs,dtp.type;

上面这个sql就是统计出不同工具名称的各个状态的数量，按工具名称进行分组统计