The EXECUTE statement executes a prepared SQL statement.
This statement can only be embedded in an application program,
SQL function, SQL procedure, or trigger. It is an executable statement that
cannot be dynamically prepared. It must not be specified in Java™.
The authorization rules are those defined for the SQL statement specified
by EXECUTE. For example, see the description of INSERT for the authorization
rules that apply when an INSERT statement is executed using EXECUTE.
The authorization ID of the statement is the run-time authorization ID
unless DYNUSRPRF(*OWNER) was specified on the CRTSQLxxx command when the program
was created. For more information, see Authorization IDs and authorization names.
>>-EXECUTE--statement-name-------------------------------------->
>--+-----------------------------------+-----------------------><
| .-,--------. |
| V | |
+-USING----variable-+---------------+
+-SQL-descriptors-------------------+
'-USING DESCRIPTOR--descriptor-name-'
SQL-descriptors:
|--+------------------------------------------------------------+-->
| .-SQL-. .-LOCAL--. |
'-INTO--+-----+--DESCRIPTOR--+--------+--SQL-descriptor-name-'
'-GLOBAL-'
>--+------------------------------------------------------------------+--|
| (1) |
| .-SQL------. .-LOCAL--. |
'-USING--+----------+--DESCRIPTOR--+--------+--SQL-descriptor-name-'
'-GLOBAL-'
Notes:
- If an SQL descriptor is specified in the USING clause and the INTO
clause is not specified, USING DESCRIPTOR is not allowed and USING SQL DESCRIPTOR
must be specified.
- statement-name
- Identifies the prepared statement to be executed. Statement-name must identify a statement that was previously prepared. The prepared
statement cannot be a SELECT statement.
- USING
- Introduces a list of variables whose values are substituted for the
parameter markers (question marks) in the prepared statement. For an explanation
of parameter markers, see PREPARE. If the prepared statement
includes parameter markers, the USING clause must be used. USING is ignored
if there are no parameter markers.
- variable,...
- Identifies one of more host structures or variables that must be declared
in the program in accordance with the rules for declaring host structures
and variables. A reference to a host structure is replaced by a reference
to each of its variables. The number of variables must be the same as the
number of parameter markers in the prepared statement. The nth variable corresponds to the nth parameter
marker in the prepared statement.
- SQL-descriptors
-
- INTO
- Identifies an SQL descriptor which contains valid descriptions of the
output variables to be used with the EXECUTE statement. This clause is only
valid for a CALL or VALUES INTO statement. Before the EXECUTE statement is
executed, a descriptor must be allocated using the ALLOCATE DESCRIPTOR statement.
- 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.
- USING
- Identifies an SQL descriptor which contains valid descriptions
of the input variables to be used with the EXECUTE statement. Before the EXECUTE
statement is executed, a descriptor must be allocated using the ALLOCATE DESCRIPTOR
statement.
- LOCAL
- Specifies the scope of the name of the descriptor to be local to program
invocation. The information is returned from the descriptor known in this
local scope.
- GLOBAL
- Specifies the scope of the name of the descriptor to be global to the
SQL session. The information is returned from the descriptor known to any
program that executes using the same database connection.
- SQL-descriptor-name
- Names the SQL descriptor. The name must identify a descriptor that already
exists with the specified scope.
- DESCRIPTOR descriptor-name
- Identifies an SQLDA that must contain a valid description of variables.
Before the EXECUTE statement is processed, the user must set the following
fields in the SQLDA. (The rules for REXX are different. For more information,
see the Embedded SQL Programming book.)
- SQLN to indicate the number of SQLVAR occurrences provided in the SQLDA.
- SQLDABC to indicate the number of bytes of storage allocated for the SQLDA.
- SQLD to indicate the number of variables used in the SQLDA when processing
the statement.
- SQLVAR occurrences to indicate the attributes of the variables.
The SQLDA must have enough storage to contain all SQLVAR occurrences.
If LOBs or distinct types are present in the results, there must be additional
SQLVAR entries for each parameter. For more information about the SQLDA, which
includes a description of the SQLVAR and an explanation on how to determine
the number of SQLVAR occurrences, see Appendix D. SQLDA (SQL descriptor area).
SQLD must
be set to a value greater than or equal to zero and less than or equal to
SQLN. It must be the same as the number of parameter markers in the prepared
statement. The nth variable described by the SQLDA
corresponds to the nth parameter marker in the prepared
statement.
Note that RPG/400® does not provide the function for setting pointers.
Because the SQLDA uses pointers to locate the appropriate variables, you have
to set these pointers outside your RPG/400 application.
Parameter marker replacement: Before the prepared
statement is executed, each parameter marker in the statement is effectively
replaced by its corresponding variable. The replacement of a parameter marker
is an assignment operation in which the source is the value of the variable,
and the target is a variable within the database manager. For a typed parameter
marker, the attributes of the target variable are those specified by the CAST
specification. For an untyped parameter marker, the attributes of the target
variable are determined according to the context of the parameter marker.
For the rules that affect parameter markers, see Table 74.
Let V denote a variable that corresponds to parameter marker P. The value
of V is assigned to the target variable for P in accordance with the rules
for assigning a value to a column. Thus:
- V must be compatible with the target.
- If V is a number, the absolute value of its integral part must not be
greater than the maximum absolute value of the integral part of the target.
- If the attributes of V are not identical to the attributes of the target,
the value is converted to conform to the attributes of the target.
- If the target cannot contain nulls, the value of V must not be null.
However, unlike the rules for assigning a value to a column:
- If V is a string, the value will be truncated (without an error), if its
length is greater than the length attribute of the target.
When the prepared statement is executed, the value used in place of P is
the value of the target variable for P. For example, if V is CHAR(6) and the
target is CHAR(8), the value used in place of P is the value of V padded with
two blanks.
This example of portions of a COBOL program shows how an INSERT statement
with parameter markers is prepared and executed.
EXEC SQL BEGIN DECLARE SECTION END-EXEC.
77 EMP PIC X(6).
77 PRJ PIC X(6).
77 ACT PIC S9(4) COMP-4.
77 TIM PIC S9(3)V9(2).
01 HOLDER.
49 HOLDER-LENGTH PIC S9(4) COMP-4.
49 HOLDER-VALUE PIC X(80).
EXEC SQL END DECLARE SECTION END-EXEC.
.
.
.
MOVE 70 TO HOLDER-LENGTH.
MOVE "INSERT INTO EMPPROJACT (EMPNO, PROJNO, ACTNO, EMPTIME)
- "VALUES (?, ?, ?, ?)" TO HOLDER-VALUE.
EXEC SQL PREPARE MYINSERT FROM :HOLDER END-EXEC.
IF SQLCODE = 0
PERFORM DO-INSERT THRU END-DO-INSERT
ELSE
PERFORM ERROR-CONDITION.
DO-INSERT.
MOVE "000010" TO EMP.
MOVE "AD3100" TO PRJ.
MOVE 160 TO ACT.
MOVE .50 TO TIM.
EXEC SQL EXECUTE MYINSERT USING :EMP, :PRJ, :ACT, :TIM END-EXEC.
END-DO-INSERT.
.
.
.
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