将字符串YYYY-MM转换为日期YYYY-MM-DD

Question

I have a set of data below and they are all in string.

EndDate
--------
2017-04

2017-02
2017-01
2017-03

2017-06

I would like to add the last date of the month into it.

EndDate
--------
2017-04-30

2017-02-28
2017-01-31
2017-03-31

2017-06-30

I'm thinking to convert them to date first and use EOMONTH syntax to give the last date of the month. However I have tried to convert the data to date using convert(datetime, EndDate) and it fails.

I tried a the syntax below from a post in stackoverflow however it gives me error message as well.

EOMONTH(CONVERT(VARCHAR(max),CAST(EndDate + '01' AS DATETIME),120))

FYI, the blank value should remain in the column.

I'm using SQL Server 2012

Thanks all for your help.

Answer 1

You were close!

SELECT EOMONTH(TRY_CONVERT(date, EndDate + '-01', 120)) FROM ...

The date style 120 is yyyy-mm-dd, but you were creating a value that was yyyy-mmdd. Also, you were passing a varchar into EOMONTH when you should just give it a date parameter.

Answer 2

我认为应该这样做：

CASE WHEN ISNULL(EndDate, '') <> '' THEN EOMONTH(CAST(EndDate + '-01' AS DATETIME)) ELSE EndDate END