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PeriRDB User’s Guide

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Column Characteristics

Data Type and Length

Each column has at least two characteristics: its data type and its length.

If the column has the NUMBER data type, it can have the additional characteristics of

precision and scale.

For example, a column with characteristics NUMBER (9,2) has a total of nine digits,

two of which are to the right of the decimal point.

NOT NULL (Oracle) and null (Sybase)

For an Oracle RDBMS, SQL uses "NOT NULL" to indicate a column that must be

filled with a value in every row—that is, NULL or no value is not a valid entry.

For a Sybase RDBMS, SQL uses "null" to indicate a column where NULL or no value

is a valid entry.

Key Type

The table definition can include columns designated as primary or foreign keys:

• a primary key is a column that uniquely identifies each row in the table

• a foreign key is a column that is a primary key in another table

PeriSQL displays these columns marked by distinctive glyphs:

Character Meaning

data type Each RDBMS uses a different naming convention to describe the

data type. For example, with an Oracle RDBMS, data type can be:

CHAR. An alphanumeric string with maximum length 255

DATE. Year, month, day, hour, seconds

LONG RAW. A byte string with fixed length 65535

LONG. An alphanumeric string with fixed length 65535

RAW. A byte string with maximum length 255

VARCHAR2. An alphanumeric string with maximum length 255

NUMBER. Decimal value

length The longest item that can be stored in the column.

Character Meaning

precision Determines the number of significant digits in the

numeric value.

scale Determines the placement of the decimal point.

Primary key

Foreign key

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Avaya Business Communications Manager - PeriRDB Bedienungsanleitung Seite 24