PREPARE — prepare a statement for execution
PREPAREprepared_nameFROMstring
PREPARE prepares a statement dynamically specified as a string for execution. This is different from the direct SQL statement PREPARE, which can also be used in embedded programs. The EXECUTE command is used to execute either kind of prepared statement.
prepared_nameAn identifier for the prepared query.
stringA literal string or a host variable containing a preparable SQL statement, one of SELECT, INSERT, UPDATE, or DELETE. Use question marks (?) for parameter values to be supplied at execution.
In typical usage, the string is a host variable reference to a string containing a dynamically-constructed SQL statement. The case of a literal string is not very useful; you might as well just write a direct SQL PREPARE statement.
If you do use a literal string, keep in mind that any double quotes you might wish to include in the SQL statement must be written as octal escapes (\042) not the usual C idiom \". This is because the string is inside an EXEC SQL section, so the ECPG lexer parses it according to SQL rules not C rules. Any embedded backslashes will later be handled according to C rules; but \" causes an immediate syntax error because it is seen as ending the literal.
char *stmt = "SELECT * FROM test1 WHERE a = ? AND b = ?"; EXEC SQL ALLOCATE DESCRIPTOR outdesc; EXEC SQL PREPARE foo FROM :stmt; EXEC SQL EXECUTE foo USING SQL DESCRIPTOR indesc INTO SQL DESCRIPTOR outdesc;
PREPARE is specified in the SQL standard.
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