如果我在一个表上只有一个非聚集索引，那么写入时所包含的列数是否会改变速度？

Question

On the exact same table, if I was to put one index on it, either:

CREATE INDEX ix_single ON MyTable (uid asc) include (columnone)

or:

CREATE INDEX ix_multi ON MyTable (uid asc) include (
    columnone,
    columntwo,
    columnthree,
    ....
    columnX
)

Would the second index cause an even greater lag on how long it takes to write to the table than the first one? And why?

Answer 1

Included columns will need more diskspace as well as time on data manipulation...

If there is a clustered index on this table too (ideally on a implicitly sorted column like an IDENTITY column to avoid fragmentation) this will serve as fast lookup on all columns (but you must create the clustered index before the other one...)

To include columns into an index is a usefull approach in extremely performance related issues only...