查找具有零类别的单位

Question

我在SQL命令之后查找没有类别的单位。下面是表：

单位

id name 

UnitCategory

id name 

UnitCategoryIndex

id categoryid unitid 

ŧ汉克斯！

Answer 1

仔细检查语法（我写它的SQL Server）。

SELECT u.id, u.name 
FROM Unit as u 
LEFT JOIN UnitCategoryIndex as uci 
ON u.id = uci.UnitId 
where uci.id is null 

Answer 2

SELECT id FROM Unit WHERE NOT EXISTS (SELECT 1 FROM UnitCategoryIndex WHERE Unit.id = UnitCategoryIndex.unitid) 

Answer 3

select * 
    from unit U 
where not exists (select * 
         from unitcategoryindex X 
        where X.unitid = U.id 
       )