小编Myu*_*ran的帖子

我有一个日期列有一些NULL.我想按日期栏ASC订购,但我需要将NULLs放在底部.如何在TSQL上做到这一点？

我有一个[Color]列,包含'Black','Red',NULL,'WW','RR'

我想要一个应该有的专栏

if color black then 'B'
if color red then 'r'
if color is Null then 'Empty'
for all other entries 'n/a'

我正在使用follwoing,但它显示错误

SELECT Name,
        CASE color
            WHEN 'black' THEN 'b'
            WHEN 'red' THEN 'r'
            WHEN ISNULL(color, 'empty')
            else 'n/a'
           END AS Color_code
FROM SalesLT.Product;

我不明白下面给出的两种编码之间的区别.第一个用于WHERELEFT JOIN.第二个代码使用AND.我不明白从每个编码中得到的输出是什么？

SELECT c.FirstName, c.LastName, oh.SalesOrderNumber
FROM SalesLT.Customer AS c
LEFT OUTER JOIN SalesLT.SalesOrderHeader AS oh
ON c.CustomerID = oh.CustomerID 
WHERE oh.SalesOrderNumber IS NULL 
ORDER BY c.CustomerID;


SELECT c.FirstName, c.LastName, oh.SalesOrderNumber
FROM SalesLT.Customer AS c
LEFT OUTER JOIN SalesLT.SalesOrderHeader AS oh
ON c.CustomerID = oh.CustomerID  
AND oh.SalesOrderNumber IS NULL 
ORDER BY c.CustomerID;