tsql - SQL Server 2012 中的联接表查询

Question

我有两个如下表：

TableA --> categoryId(pk), categoryParentId, catName
TableB --> empId(pk), categoryId, empName, empDesignation

我想从其中of等于of中获取catName具有相应 categoryId 的所有内容。请帮忙。TableAcategoryId=2TableBcategoryParentId=2TableA

结果：

1002   SE
1003   MD

Answer 1

我希望这个查询能满足您的需求

    SELECT TABLEA.CATNAME AS CATEGORY
    from TABLEB INNER JOIN TABLEA 
    ON TABLEA.CATEGORYPARENTID = TABLEB.CATEGORYID

Answer 2

Something like this?

SELECT DISTINCT catName FROM TABLEA WHERE categoryParentId IN (SELECT DISTINCT categoryID from TABLEB);

Answer 3

解决方案INNER JOIN：

select TableA.catName
from TableA
inner join TableB on TableA.categoryParentId = TableB.categoryId

UsingINNER JOIN是用于连接表的推荐方法（而不是SELECT ... FROM TableA, TableB ...）

看：

• INNER JOIN ON vs WHERE 子句
  （这个问题实际上是关于MySql，但答案说它与SQL Server 相同）
• SQL Server 中 INNER 联接和笛卡尔联接的区别

---

回答您的评论（我假设您想要categoryIdfrom TableA）：

select TableA.catName, TableA.categoryId
from TableA
inner join TableB on TableA.categoryParentId = TableB.categoryId
where TableB.categoryId = 2

Answer 4

另一种方法...

SELECT 
  catname
from
  tablea a INNER JOIN
  tableb b ON 
    a.categoryParentID = b.categoryID
  group by
  catname

Answer 5

This should do the trick

SELECT tableA.catName
 FROM tableA, tableB
WHERE tableB.categoryId = table1.categoryParentId
  AND tableB.categoryId = 2;

If you want the unique catNames, you can use

SELECT distinct tableA.catName
 FROM tableA, tableB
WHERE tableB.categoryId = table1.categoryParentId
  AND tableB.categoryId = 2;