如果在T-SQL中记录为NULL，如何替换字符串

I'm writing a T-SQL report that shows the number of accounts that are in different statuses for different customers. The report results in something like:

我正在撰写一份T-SQL报告，显示不同客户处于不同状态的帐户数量。报告结果如下：

Customer1    NoService        7
Customer1    IncompleteOrder  13
Customer1    NULL             9
Customer2    NoService        12
Customer2    Available        19
Customer2    NULL             3
...

The 'NULL' status is valid data, but instead of displaying NULL, I want to display "Pending". Here is my SQL so far:

'NULL'状态是有效数据，但我想显示“Pending”而不是显示NULL。到目前为止，这是我的SQL：

USE cdwCSP;
SELECT
   sr.sales_region_name   AS SalesRegion
   , micv.value
   , COUNT(sr.sales_region_name)
FROM prospect p
   LEFT JOIN sales_region sr
     ON p.salesRegionId = sr.sales_region_number
   LEFT JOIN prospectOrder po
     ON po.prospectId = p.prospectId
   LEFT JOIN wo
     ON wo.prospectId = p.prospectId
   LEFT JOIN woTray wot
     ON wot.woId = wo.woId
   LEFT JOIN miscInformationCustomerCategory micc
     ON micc.prospectId = p.prospectId
   LEFT JOIN miscInformationCustomerValues micv
     ON micv.miscInformationCustomerCategoryId = micc.miscInformationCustomerCategoryId
   LEFT JOIN miscInformationCategory mic
     ON micc.miscInformationCategoryId = mic.miscInformationCategoryId
WHERE wot.dateOut IS NULL
     AND mic.categoryName LIKE '%Serviceability%'
GROUP BY sr.sales_region_name, micv.value
ORDER BY sr.sales_region_name, micv.value;

Any help would be appreciated, I'm still learning T-SQL so this might be an easy question to answer.

任何帮助将不胜感激，我仍然在学习T-SQL，所以这可能是一个容易回答的问题。

3 个解决方案

#1

You can use COALESCE or ISNULL. The former is standard and returns the first NOT NULL argument (or NULL if all arguments are NULL)

您可以使用COALESCE或ISNULL。前者是标准的并返回第一个NOT NULL参数（如果所有参数都为NULL，则返回NULL）

SELECT COALESCE(micv.value,'Pending') as value

ISNULL is restricted to only 2 arguments but is more efficient in SQL Server if the first value to be tested is expensive to evaluate (e.g. a subquery).

ISNULL仅限于2个参数，但如果要测试的第一个值很昂贵（例如子查询），则SQL Server中的效率更高。

One potential "gotcha" with ISNULL to be aware of is that it returns the datatype of the first parameter so if the string to be substituted is longer than the column datatype would allow you will need a cast.

ISNULL要注意的一个潜在“问题”是它返回第一个参数的数据类型，因此如果要替换的字符串比列数据类型允许的话，则需要进行强制转换。

E.g.

例如。

CREATE TABLE T(C VARCHAR(3) NULL);

INSERT T VALUES (NULL);

SELECT ISNULL(C,'Unknown')
FROM T

Would return Unk

将返回Unk

But ISNULL(CAST(C as VARCHAR(7)),'Unknown') or COALESCE would both work as desired.

但ISNULL（CAST（C as VARCHAR（7）），'Unknown'）或COALESCE都可以按预期工作。

#2

you can also use ISNULL('value', 'replacewithvalue')

你也可以使用ISNULL（'value'，'replacewithvalue'）

#3

SELECT
   sr.sales_region_name   AS SalesRegion
   , ISNULL(micv.value,'Pending')
   , COUNT(sr.sales_region_name)
FROM prospect p
--(...)

Go check ISNULL for further info.

请查看ISNULL以获取更多信息。

#1