Description
- statement-name
- Identifies the prepared statement. When the DESCRIBE statement is executed,
the name must identify a prepared statement at the application server.
If the prepared statement is a SELECT or VALUES INTO statement, the information
returned describes the columns in its result table. If the prepared statement
is a CALL statement, the information returned describes the OUT and INOUT
parameters of the procedure.
- USING
- Identifies an SQL descriptor.
- LOCAL
- Specifies the scope of the name of the descriptor to be local to program
invocation.
- GLOBAL
- Specifies the scope of the name of the descriptor to be global to the
SQL session.
- SQL-descriptor-name
- Names the SQL descriptor. The name must identify a descriptor that already
exists with the specified scope.
- INTO descriptor-name
- Identifies an SQL descriptor area (SQLDA), which is described in Appendix D. SQLDA (SQL descriptor area). Before the DESCRIBE statement is executed, the following
variable in the SQLDA must be set.
- SQLN
- Indicates the number of SQLVAR entries provided in the SQLDA. SQLN must
be set to a value greater than or equal to zero before the DESCRIBE statement
is executed. For information on techniques to determine the number of occurrences
requires, see Determining how many SQLVAR occurrences are needed.
The rules for REXX are different. For more information, see the Embedded SQL Programming book.
When the DESCRIBE statement is executed, the database manager assigns values
to the variables of the SQLDA as follows:
- SQLDAID
- The first 6 bytes are set to 'SQLDA ' (that is, 5 letters followed by
the space character).
The seventh byte is set based on the result columns
described:
- If the SQLDA contains two, three, or four SQLVAR entries for
every select list item (or, column of the result table), the seventh byte
is set to '2', '3', or '4'. This technique is used in order to accommodate
LOB or distinct type result columns, labels, and system names.
- Otherwise, the seventh byte is set to the space character.
The seventh byte is set to the space character if there is not
enough room in the SQLDA to contain the description of all result columns.
The eighth byte is set to the space character.
- SQLDABC
- Length of the SQLDA in bytes.
- SQLD
- If the prepared statement is a SELECT, SQLD is set to the
number of columns in its result table. If the prepared statement is a CALL
statement, SQLD is set to the number of OUT and INOUT parameters of the procedure.
Otherwise, SQLD is set to 0.
- SQLVAR
- If the value of SQLD is 0, or greater than the value of SQLN, no values
are assigned to occurrences of SQLVAR.
If the value of SQLD
is n, where n is greater than
0 but less than or equal to the value of SQLN, values are assigned to the
first n occurrences of SQLVAR so that the first occurrence
of SQLVAR contains a description of the first column of the result table (or
parameter), the second occurrence of SQLVAR contains a description of the
second column of the result table (or parameter), and so on. For information
on the values assigned to SQLVAR occurrences, see Field descriptions in an occurrence of SQLVAR.
- USING
- Specifies what value to assign to each SQLNAME variable in
the SQLDA. If the requested value does not exist or if the length of a name
is greater than 30, SQLNAME is set to a length of 0.
- NAMES
- Assigns the name of the column (or parameter). This is the
default. For the DESCRIBE of a prepared statement where the name is explicitly
listed in the select-list, the name specified is returned. The column name
returned is case sensitive and without delimiters.
- SYSTEM NAMES
- Assigns the system column name of the column.
- LABELS
- Assigns the label of the column. (Column labels are defined by the LABEL
statement.) Only the first 20 bytes of the label are returned.
- ANY
- Assigns the column label. If the column has no label, the column name
is used instead.
- BOTH
- Assigns both the label and name of the column. In this case, two or
three occurrences of SQLVAR per column, depending on whether the result set
contains distinct types, are needed to accommodate the additional information.
To specify this expansion of the SQLVAR array, set SQLN to 2*n or 3*n(where n is the
number of columns in the table or view). The first n occurrences
of SQLVAR contain the column names. Either the second or third n occurrences contain the column labels. If there are no distinct types,
the labels are returned in the second set of SQLVAR entries. Otherwise, the
labels are returned in the third set of SQLVAR entries.
- ALL
- Assigns the label, column name, and system column name. In
this case three or four occurrences of SQLVAR per column, depending on whether
the result set contains distinct types, are needed to accommodate the additional
information. To specify this expansion of the SQLVAR array, set SQLN to 3*n or 4*n (where n is the number of columns in the result table). The first n occurrences of SQLVAR contain the system column names. The second or
third n occurrences contain the column labels. The
third or fourth n occurrences contain the column names
if they are different from the system column name. Otherwise the SQLNAME field
is set to a length of zero. If there are no distinct types, the labels are
returned in the second set of SQLVAR entries and the column names are returned
in the third set of SQLVAR entries. Otherwise, the labels are returned in
the third set of SQLVAR entries and the column names are returned in the fourth
set of SQLVAR entries.
(C) Copyright IBM Corporation 1992, 2006. All Rights Reserved.