Question

I have a table with a dateTime column on which I want to put a filtered index. This index will get rebuilt each week. Each time it’s rebuilt, I want it to include rows two days old and newer, based on this column. Can I create such a filtered index? I’ve tried various approaches and I get syntax errors.

For example, the following Where clause on the index creation did not work:

WHERE (ReadTime > DateAdd(dd,-2,GetDate()))

Answer 1

You can’t do this by referencing getdate() directly. You would need dynamic SQL.

The CREATE INDEX grammar only allows comparisons against a constant.

CREATE [ UNIQUE ] [ CLUSTERED | NONCLUSTERED ] INDEX index_name 
    ON <object> ( column [ ASC | DESC ] [ ,...n ] ) 
    [ INCLUDE ( column_name [ ,...n ] ) ]
    [ WHERE <filter_predicate> ]
    ... /*Irrelevant grammar removed*/

<filter_predicate> ::= 
    <conjunct> [ AND <conjunct> ]

<conjunct> ::=
    <disjunct> | <comparison>

<disjunct> ::=
        column_name IN (constant ,...n)

<comparison> ::=
        column_name <comparison_op> constant

<comparison_op> ::=
    { IS | IS NOT | = | <> | != | > | >= | !> | < | <= | !< }