將日期轉換爲varchar，然後將其轉換回日期

Question

我正在研究別人編寫和看到過的T-SQL查詢。

AND Cast(m.MeasurementDateTime as date) >= cast('''+cast(@StartDate as varchar(100)) + ''' as date) 
AND cast(m.MeasurementDateTime as date) <= cast('''+cast(@EndDate as varchar(100)) + ''' as date)' 

爲什麼有人會這樣做？我錯過了什麼嗎？它與

CAST(@StartDate AS DATE) 

對不對？ @EndDate和@StartDate來自一個報告，所以我不是源數據類型。

Answer 1

你能打印@StartDate來查看它的格式嗎？如果有例如整數格式，我們不能直接施放到一個日期：

select cast(20031016 as date) 
Explicit conversion from data type int to date is not allowed. 

select cast(cast(20031016 as varchar) as date) 
16.10.2003 00:00:00