mysql语言中取季度,如何从SQL中的日期字段中提取月份

I have a date field name as "InvoiceDate" in my table that have a date information like this "20140231", I want to get the month out of that date field so that I can group my record per quarter see the attached query that I tried, currently the date field is hard coded as you see on the query.

Can you please help how can I get the month on this record"20140231",

What I have tried:

This what I tried SELECT TOP 1000 [Advise no]

,[Amount]

,[Date]

,[Bas Fund Description]

,[Invoice Date]

(MONTH, DATEDIFF(MONTH, 0, [Invoice Date]), 0) AS months

, CASE WHEN [Invoice Date] BETWEEN 20170401 AND 20170631

THEN 'Q1'

WHEN [Invoice Date] BETWEEN 20170701 AND 20170931

THEN 'Q2'

WHEN [Invoice Date] BETWEEN 20171001 AND 20171231

THEN 'Q3'

WHEN [Invoice Date] BETWEEN 20180101 AND 20180331

THEN 'Q4'

WHEN [Invoice Date] Is Null

THEN 'Null'

END AS QuarterPeriod

,[Valuation Date]

,[qgs_geometry]

,[qgs_fid]

,[ProvinceName]

FROM [DOD].[dbo].[View_DPW_PACE]

解决方案