Column type characteristics

DBMS has a rich set of column types.

The Store database implementation supports all column types, and any column type can be nullable or marked as not-null.

All numeric and date/time columns are fixed width, though Null values will take no extra storage space in the database. See TDbColType for the characteristics of fixed width column types.

Text and Binary columns are all variable length.

The short column types Text8, Text16 and Binary support the maximum length attribute, and can only store up to 255 units (characters or bytes) of data. If KDbUndefinedLength is specified as the maximum length attribute for these column types when a table is created, they are given a maximum length of 255.

Long column types LongText8, LongText16 and LongBinary can theoretically store up to 2GB of data depending on resources available in the store, at the cost of a little more storage overhead than short columns.

A Null variable length column is one with no data in it, in particular DBMS does not distinguish between a zero-length Text column and a Null value Text column. See TDbColType for the characteristics of the variable width column types.

See also:

• Database storage overhead