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ESQL elements and statements
Examples The first example is a code fragment from the DynUpd function in sample program 3DynUpd.pc,
which illustrates dynamic processing of an UPDATE statement:
340
Syntax
{ :host_variable | quoted_literal }
/*
** Process a dynamic non-SELECT input statement
** PREPARE the statement
** EXECUTE the prepared statement
** COMMIT WORK
*/
EXEC SQL PREPARE dynstmt FROM :sql_stmt_v ;
EXEC SQL EXECUTE dynstmt ;
EXEC SQL COMMIT WORK ;
This example is a code fragment from the DynSel function in sample program 4DynSel.pc,
which illustrates dynamic processing of a SELECT statement:
/*
** PREPARE a the dynamic SELECT statement.
** DECLARE cursor for the prepared SELECT statement.
** NOTE: You must set input parameter values before OPEN CURSOR.
** If your query has input parameters, you must define them in
** the DECLARE SECTION.
** OPEN the declared cursor.
** NOTE: For static statements, if a DECLARE CURSOR
** statement contains references to automatic variables,
** the OPEN CURSOR statement must be in the same C function.
**
** Name WHENEVER routine for NOT FOUND condition.
** FETCH a row and print results until no more rows.
*/
EXEC SQL PREPARE stmtid from :sel_stmt_v ;
EXEC SQL DECLARE dyncur CURSOR FOR stmtid ;
EXEC SQL OPEN dyncur ;
EXEC SQL WHENEVER NOT FOUND GOTO seldone ;
Notes • A statement string can have one or more references to input variables. These variables
represent values supplied at run time to:
– INSERT and UPDATE statements
– Predicates in DELETE, UPDATE, and SELECT statements
• A program supplies an input variable to a PREPARE statement either as a substitution name
or as a parameter marker. For example:
– A substitution name is a name preceded by a colon ( : ) in a statement string. This
name does not refer to a C Language variable, but acts only as a placeholder for input
variables.
– A parameter marker is a question mark ( ? ) in the statement string, serving as a
placeholder for input variables.