oracle - Will nulling bad data reduce index sizes? -


i've got oracle siebel database subject of data cleansing exercise.

in s_contact table there load of invalid email addresses replaced either null or empty string.

as understand it, activity not reduce size of table, due being fixed length column.

however, activity reduce size of indexes?

that is, replacing few million "no email" / "asdf" / "no@email.com" values blanks or nulls (i led believe blanks , nulls same in oracle).

oracle treats empty strings null.

take @ link: null vs empty string in oracle

null values, rule of thumb, never indexed, yes, reduce size of index, if nullable column column on said index.

if wanted index null values, have either create function based index using nvl (and adjust queries accordingly), or create , index on ([fixed value],[nullable column])

[edit] pointed out @a_horse_with_no_name , "tuples containing null values never indexed", meant say, way clearer.


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