Sybase 12.4.2 Adaptive Server IQ index types, Combining index types, 144, Mix of valid indexes

Adaptive Server IQ index types

•VARCHAR data with more than 255 bytes

HNG indexes do not allow FLOAT, REAL, or DOUBLE data.

All other data types are supported in all index types.

If you try to create an index on a column that contains VARCHAR data greater than 255 bytes, you get this error message:

An index cannot be created on a varchar column greater than 255 characters.

Combining index types

If a column is going to be used in more than one type of query, multiple column index types might be appropriate. The following table shows which index types make good combinations.

Table 4-4: Mix of valid indexes

		Add Index
Existing Index		HG	HNG	LF
HG		-	1	2
HNG		1	-	1
LF		2	1	-
1	= A reasonable combination
2	= An unlikely combination

Note The High_Group index in Adaptive Server IQ Version 12.0 differs from earlier versions. For some columns you may want both High_Group and High_Non_Group; previously, it did not make sense to have both.

Adaptive Server IQ index types

This section explores in depth the reasons you might use each of the column index types.

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