ABAP透明表里的时间戳，数据类型为dec：
有个需求：计算这两个时间戳之间的天数间隔，丢弃时间戳年-月-日8位后面的小时：分钟：秒。
举个例子：如果时间戳是20180918173132，丢弃173132，只保留20180918, 然后再计算天数间隔。
直接用CDS view的字符串操作函数substring是不行的，因为时间戳类型dec和substring期待的字符串类型不匹配。
解决方案：
先将时间戳字段类型从dec强制转换成abap.dats：
@AbapCatalog.sqlViewName: 'zproday'
@AbapCatalog.compiler.compareFilter: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: 'Day between'
define view zdate_day_between as select from comm_product {
key comm_product.product_id as prod_id,
comm_product.product_guid as prod_guid,
comm_product.valid_from as valid_from,
comm_product.valid_to as valid_to,
cast(substring(cast(valid_from as abap.char(32)),1,8) as abap.dats) as from_date,
cast(substring(cast(valid_to as abap.char(32)),1,8) as abap.dats) as to_date
}然后再用CDS view标准的时间处理函数DATS_DAYS_BETWEEN:
@AbapCatalog.sqlViewName: 'zdbetw'
@AbapCatalog.compiler.compareFilter: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: 'Day between'
define view zc_date_day_between as select from zdate_day_between as host{
key host.prod_guid,
host.prod_id,
host.from_date,
host.to_date,
DATS_DAYS_BETWEEN(host.from_date, host.to_date) as no_of_days
}测试结果：
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