问题
I have a 12 varchar(50) fields in a table of about 90 million rows that I need to increase to varchar(100) in length. Each of these fields has an index (with only the one field as a member). If I increase the length of the varchar fields, will the indexes either need to be rebuilt (or would be rebuilt automatically), or would the statistics become out of date?
I don't have a reasonably sized test system test (or perhaps dont know how to see if the indexes were rebuilt or statistics need to be recomputed).
Thanks
回答1:
Statistics are based on what is in columns, not their size, so your statistics won't become out of date.
Bear in mind that sometimes when you alter a column, SQL server will add a new column to the table and drop the existing one, so it will have to rebuild the index in that case anyway.
Despite searching I can't categorically say whether you have to rebuild indexes, but I would rebuild regardless (as this should be occuring as part of your normal maintenance, assuming this table is not read-only or very low writes)
BTW, having a seperate index on each of those columns might not be optimal. Have you profiled your query workload?
来源：https://stackoverflow.com/questions/3868911/sql-server-2005-index-rebuild-when-increasing-the-size-of-a-varchar-field