我想知道是否有可能检索类似于cdc.fn_cdc_get_net_changes_<capture_instance>(from_lsn , to_lsn, 'all with mask')的表的净变化，这些表没有主键，但确实有一个约束来确保一个（或多个）列是
答案 0 :(得分：0)
花了我一段时间，但我认为我有一个可行的解决方案，请告诉我是否有更好的解决方案，或者您是否发现自己的错误。
我们假设一个名为capture_instance的表的捕获实例具有唯一列ID和非唯一列field1，field2和field3以及变量{ {1}}和@from_lsn。
@to_lsn要完全匹配WITH
cdc_all AS (
-- Retrieve the change table with all changes
SELECT *
FROM cdc.fn_cdc_get_all_changes_capture_instance(@from_lsn, @to_lsn, 'all')
),
f AS (
SELECT cdc_all.*, ops.[delete], ops.[insert], ops.[update], ops.[net_op]
FROM cdc_all
INNER JOIN (
-- Retrieve three flags for insert, update and delete and the net operation
-- also filter insert + delete pairs because it results in no change
SELECT *
FROM (
SELECT ID
, MAX(CASE WHEN __$operation = 1 THEN 1 ELSE 0 END) as [delete]
, MAX(CASE WHEN __$operation = 2 THEN 1 ELSE 0 END) as [insert]
, MAX(CASE WHEN __$operation = 4 THEN 1 ELSE 0 END) as [update]
, MIN(__$operation) [net_op]
FROM cdc_all
GROUP BY ID
) ops
WHERE NOT (ops.[delete] = 1 AND ops.[insert] = 1)
) ops ON cdc_all.ID = ops.ID
)
SELECT net.[max_lsn], f.[net_op] __$operation
, (CASE WHEN net.__$update_mask != 0x0 THEN net.__$update_mask ELSE NULL END) __$update_mask
, f.[ID], [field1], [field2], [field3]
FROM f
INNER JOIN (
-- bitwise OR the __$update_mask of the updates
-- also retrieve the last lsn of each row which should be used as the __$start_lsn of the result set
SELECT ID
, CAST(SUM(DISTINCT CAST((CASE WHEN f.[__$operation] = 4 AND f.[insert] != 1 THEN f.[__$update_mask] ELSE 0 END) as int)) as varbinary(2)) [__$update_mask]
, MAX(__$start_lsn) [max_lsn]
FROM f
GROUP BY ID
) net ON f.ID = net.ID AND f.__$start_lsn = net.[max_lsn]
的行为，最后使varbinary的大小尽可能小，以使所有字段都适合，但是更大的值不会破坏功能。