ben.brugman (1/7/2013)
Does this read all rows from A with a 6 in it. So RID lookup of all A = 6 rows?
No. It reads all rows from the index where A=6, filters them as it reads for C =7. Once it has all rows that match all conditions that have columns within the index, if the index is not covering the lookups are done to fetch the rest of the columns.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability