The characteristics of a field.
(B)0[mfield-attributes =
[4mDATATYPE[m IS qqq> data-type qqk
lqqqqqqqqqqqqqqqqqqqqqqqqqj
mqqwqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqwqqq>
mwqwqq> validity-clauseqqqqqqqqqqqqqqqqqqqqqqqwqwqj
x tqq> missing-value-clauseqqqqqqqqqqqqqqqqqqu x
x tqq> dtr-clauseqqqqqqqqqqqqqqqqqqqqqqqqqqqqu x
x tqq> [4mCOLLATING_SEQUENCE[m IS sequence-nameqqqu x
x mqq> [4mNO[m [4mCOLLATING_SEQUENCE[m qqqqqqqqqqqqqqqqj x
mqqqqqqqqqqqqqqqqq<qqqqqqqqqqqqqqqqqqqqqqqqqqqqj
1 – data-type
Describes the characteristics of data stored in fields. Request
the top-level HELP topic "Datatypes" for a table of Oracle Rdb data
types.
1.1 – Segmented string
(B)0[mseg-str-option =
qwqwqqq> [4mSEGMENT_LENGTH[m IS qqq> n qqq> BYTES qqwqwq>
x mqqq> [4mSUB_TYPE[m IS qqqqwqqqq> [4mBLR[m qqqqqqwqqqqj x
x tqqqq> [4mTEXT[m qqqqqu x
x mqqqq> n qqqqqqqqj x
mqqqqqqqqqqqqqqqqqqqqqq<qqqqqqqqqqqqqqqqqqqqqqqqj
2 – validity-clause
Specifies a validation check for a field. Oracle Rdb evaluates the
conditional expression at run time when the field is stored or
modified.
(B)0[mvalidity-clause =
qwq> [4mVALID[m [4mIF[m qqq> conditional-expr qwq>
mq> [4mNO[m [4mVALID[m [4mIF[m qqqqqqqqqqqqqqqqqqqqj
conditional-expr Specifies a valid conditional expression. This
conditional expression must refer only to the
field being defined. Ask for HELP on Cond_
expr for a complete description of Oracle Rdb
conditional expressions.
2.1 – Example
In the following example, the SHOW FIELD statement shows the
SEX field, which contains a VALID IF clause. The CHANGE FIELD
statement removes the VALID_IF clause from the SEX field:
RDO> DATA FILE DB$:PERSONNEL
RDO> SHOW FIELD SEX
SEX text size is 1
Description: M, F
Missing value: "?"
Valid: IF SEX = 'M' OR SEX = 'F' OR
SEX MISSING
RDO> CHANGE FIELD SEX NO VALID IF.
RDO> SHOW FIELD SEX
SEX text size is 1
Description: M, F
Missing value: "?"
RDO> ROLLBACK
3 – missing-value-clause
Specifies a numeric or character string literal that denotes that
no value is stored in the field. When you retrieve or display the
value, Oracle Rdb returns the contents of the MISSING_VALUE string
or number.
(B)0[mmissing-value-clause =
qqqqq> [4mMISSING_VALUE[m IS qqqwqqq> fxd-pnt-num qqqqqwqqq>
mqqq> quoted-string qqqj
3.1 – fxd-pnt-num
A fixed-point number that Oracle Rdb uses to replace a retrieved
null value.
A fixed-point number always includes a decimal point, even when
there are no digits to the right of the decimal point.
For example, if a field contains dollar and cent values, you
may want to use 0.00 as the missing value to preserve the value
context when Oracle Rdb retrieves and displays null values. In this
particular case, if you do not allow null values and you do not
specify a missing value, Oracle Rdb fills the retrieved field with
zeros.
Specify a number that does not exceed the defined field length
and include a decimal point.
3.2 – quoted-string
A character string that Oracle Rdb uses to replace retrieved null
values. For example, you could specify a missing value of "Value
not found" to replace null values. Specify a character string
whose length does not exceed the length of the field. Enclose
the string in single or double quotation marks ("string" or
'string'). Ask for HELP on Value_expr for a complete description
of the use of literal expressions.
3.3 – Examples
Example 1
Define missing value for dates:
DEFINE FIELD STANDARD_DATE
DESCRIPTION /* Universal date field */
DATATYPE IS DATE
MISSING_VALUE IS "17-NOV-1858 00:00:00.00"
EDIT_STRING FOR DATATRIEVE IS 'DD-MMM-YYYY'.
This definition defines a missing value for date fields to be the
same as the base date and time for OpenVMS.
Example 2
Define missing values for numeric fields:
DEFINE FIELD SALARY
DATATYPE IS SIGNED LONGWORD SCALE -2
MISSING_VALUE IS 0.00
EDIT_STRING FOR DATATRIEVE IS '$$$$,$$9.99'.
This statement specifies "0.00" as the missing value for SALARY
fields.
Example 3
Define missing values for text fields:
DEFINE FIELD ADDRESS_DATA
DATATYPE IS TEXT SIZE 20
MISSING_VALUE IS "Not available".
When you retrieve a field whose value is missing, Oracle Rdb
displays the string "Not available".
4 – dtr-clause
Oracle Rdb provides support for DATATRIEVE, the Digital query
language. You can specify one or more of the following clauses:
Query header
Query name
Default value
Edit string
If you specify a DATATRIEVE attribute on a global field, you can
cancel that attribute for a particular relation, using the NO
qualifier. The NO qualifier of the dtr-clause is available when
you are changing a definition with the CHANGE FIELD or CHANGE
RELATION statement. The NO qualifier is not used with the dtr-
clause of DEFINE FIELD, DEFINE RELATION, and DEFINE VIEW.
4.1 – Format
(B)0[mdtr-clause =
qwq> [4mQUERY_HEADER[m [4mFOR[m qqwq> DTR qqqqqqqqwqq> IS qw> quoted-string qqwqwq>
x mq> DATATRIEVE qj mqqqqqq / <qqqqqqqqj x
tq> [4mNO[m [4mQUERY_HEADER[m [4mFOR[m qqwqq DTR qqqqqqqqqqwqqqqqqqqqqqqqqqqqqqqqqqqu
x mq> DATATRIEVE qqqj x
tq> [4mQUERY_NAME[m FOR qqqqwq> DTR qqqqqqqqqwq> IS qq> quoted-string qqqqu
x mq> DATATRIEVE qqj x
tq> [4mNO[m [4mQUERY_NAME[m FOR qqqqwqq DTR qqqqqqqqqwqqqqqqqqqqqqqqqqqqqqqqqqqu
x mq> DATATRIEVE qqj x
tq> [4mDEFAULT_VALUE[m FOR qwq> DTR qqqqqqqqqwq> IS qw> fxd-pnt-num qqqqwqu
x mq> DATATRIEVE qqj m> quoted-string qqj x
tq> [4mNO[m [4mDEFAULT_VALUE[m FOR qwq> DTR qqqqqqqqqwqqqqqqqqqqqqqqqqqqqqqqqqqu
x mq> DATATRIEVE qqj x
tq> [4mEDIT_STRING[m FOR qqqwq> DTR qqqqqqqqqwq> IS qq> quoted-string qqqqu
x mq> DATATRIEVE qqj x
mq> [4mNO[m [4mEDIT_STRING[m FOR wq> DTR qqqqqqqqqwqqqqqqqqqqqqqqqqqqqqqqqqqqqqj
mq> DATATRIEVE qqj
fxd-pnt-num The default value returned to DATATRIEVE when
Oracle Rdb retrieves null values. A fixed-point
number is a number that always includes a
decimal point, even when there are no digits
to the right of the decimal point.
quoted-string A literal expression that Oracle Rdb returns to
DATATRIEVE.
4.2 – Examples
Example 1
The following example defines a field and specifies a DATATRIEVE
edit string for that field:
DEFINE FIELD MIDDLE_INITIAL
DATATYPE IS TEXT SIZE 1
EDIT_STRING FOR DATATRIEVE IS 'X.'.
The X represents any alphanumeric character. When you access
this field through DATATRIEVE, the field value is followed by a
period. The DATATRIEVE documentation set contains a complete list
of editing characters.
Example 2
The following example defines a DATATRIEVE query name for one
field and a DATATRIEVE query header for another:
DEFINE FIELD STATE
DATATYPE IS TEXT SIZE 2
QUERY_NAME FOR DATATRIEVE IS "ST".
DEFINE FIELD SEX
DATATYPE IS TEXT SIZE 1
VALID IF SEX = 'M' OR SEX = 'F'
QUERY_HEADER FOR DATATRIEVE IS "S"/"E"/"X".
These statements define DATATRIEVE query names and query headers
for the STATE and SEX fields. The header for the SEX field will
be one character wide, like the field itself.
5 – COLLATING
The COLLATING_SEQUENCE clause specifies the collating sequence to
be used in the field you are defining.
The NO COLLATING_SEQUENCE clause specifies that the field will
use the standard default collating sequence (the ASCII collating
sequence).