Declaring a DSQL Cursor
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DSQL must declare a cursor based on a user-defined SELECT statement. Usually, DSQL programs:
- Prompt the user for a query (
SELECT). - Store the query in a host-language variable.
- Issue a
PREPAREstatement that uses the host-language variable to describe the query results in anXSQLDA. - Declare a cursor using the query alias.
The complete syntax for DECLARE CURSOR in DSQL is:
DECLARE cursorname CURSOR FOR queryname;
For example, the following C code fragment declares a string variable,
querystring, to hold the user-defined query, gets a query from the user and stores it in querystring, uses querystring to PREPARE a query called QUERY, then declares a cursor, C, that uses QUERY:
. . .
EXEC SQL
BEGIN DECLARE SECTION;
char querystring [512];
XSQLDA *InputSqlda, *OutputSqlda;
EXEC SQL
END DECLARE SECTION;
. . .
printf("Enter query: "); /* prompt for query from user */
gets(querystring); /* get the string, store in querystring */
. . .
EXEC SQL
PREPARE QUERY INTO OutputSqlda FROM :querystring;
. . .
EXEC SQL
DECLARE C CURSOR FOR QUERY;
For more information about creating and filling XSQLDA structures, and preparing DSQL queries with PREPARE, see Using Dynamic SQL.