Storing column length
The collength column value depends on the data type of the column.
Integer-based data types
A collength value
for a BIGINT, BIGSERIAL, DATE, INTEGER, INT8, SERIAL, SERIAL8, or
SMALLINT column is machine-independent. The database server uses the
following lengths for these integer-based data types of the SQL language.
| Integer-based data types | Length (in bytes) |
|---|---|
| SMALLINT | 2 |
| DATE, INTEGER, and SERIAL | 4 |
| INT8 and SERIAL8 | 10 |
| BIGINT and BIGSERIAL | 8 |
Varying-length character data types
For HCL
OneDB™ columns
of the LVARCHAR type, collength has the value of max from
the data type declaration, or 2048 if no maximum
was specified.
For VARCHAR or NVARCHAR columns, the max_size and min_space values
are encoded in the collength column using one of these formulas:
- If the collength value is positive:
collength = (min_space * 256) + max_size - If the collength value is negative:
collength + 65536 = (min_space * 256) + max_size
Time data types
As noted
previously, DATE columns have a value of 4 in the collength column.
For
columns of type DATETIME or INTERVAL, collength is determined
using the following formula:
(length * 256) + (first_qualifier * 16) + last_qualifierThe
length is the physical length of the DATETIME or INTERVAL field, and first_qualifier and last_qualifier have
values that the following table shows.
| Field qualifier | Value | Field qualifier | Value |
|---|---|---|---|
| YEAR | 0 | FRACTION(1) | 11 |
| MONTH | 2 | FRACTION(2) | 12 |
| DAY | 4 | FRACTION(3) | 13 |
| HOUR | 6 | FRACTION(4) | 14 |
| MINUTE | 8 | FRACTION(5) | 15 |
| SECOND | 10 |
For example, if a DATETIME YEAR TO MINUTE column has
a length of 12 (such as YYYY:DD:MO:HH:MI),
a first_qualifier value of 0 (for YEAR), and
a last_qualifier value of 8 (for MINUTE),
then the collength value is 3080 (from (256
* 12) + (0 * 16) + 8).
Fixed-point data types
The collength value
for a MONEY or DECIMAL (p, s) column can be calculated
using the following formula:
(precision * 256) + scaleSimple-large-object data types
If the data type of the column is BYTE or TEXT, collength holds the length of the descriptor.