Question

The scenario:

Table1
CatId|Name|Description

Table2
ItId|Title|Date|CatId (foreign key)

I want to return all rows from Table1 and Title,Date from Table2, where
The returned from Table 2 must be the Latest one by the date column.
(in second table there many items with same CatId and I need just the latest)

I have 2 queries but can’t merge them together:

Query 1:  
SELECT Table1.Name,  Table1.Description,
       Table2.Title, Table2.Date
FROM 
       Table1 LEFT JOIN Table2 ON Table1.CatId=Table2.CatId

Query2:

SELECT TOP 1 Table2.Title, Table2.Date
FROM 
    Table2
WHERE 
    Table2.CatId = @inputParam
ORDER BY Table2.Date DESC

Answer 1

Sounds like you’re talking about a groupwise maximum (newest row in Table2 for each matching row in Table1), in which case, the easiest way is use ROW_NUMBER:

WITH CTE AS
(
    SELECT
        t1.Name, t1.Description, t2.Title, t2.Date,
        ROW_NUMBER() OVER (PARTITION BY t1.CatId ORDER BY t2.Date DESC) AS Seq
    FROM Table1 t1
    LEFT JOIN Table2 t2
        ON t2.CatId = t1.CatId
)
SELECT *
FROM CTE
WHERE Seq = 1
OR Date IS NULL