A single row query retrieves at most one row from the database. A single-row query SELECT statement has an INTO clause following the select list and before the FROM clause. The INTO clause contains a list of host variables to receive the value for each select list item. There must be the same number of host variables as there are select list items. The host variables may be accompanied by indicator variables to indicate NULL results.
When the SELECT statement is executed, the database server retrieves the results and places them in the host variables. If the query results contain more than one row, the database server returns an error.
If the query results in no rows being selected, a Row Not Found
warning is returned. Errors and warnings are returned in the SQLCA structure. See The SQL Communication Area (SQLCA).
The following code fragment returns 1 if a row from the Employees table is fetched successfully, 0 if the row doesn't exist, and -1 if an error occurs.
EXEC SQL BEGIN DECLARE SECTION; long ID; char name[41]; char Sex; char birthdate[15]; short int ind_birthdate; EXEC SQL END DECLARE SECTION; ... int find_employee( long Employees ) { ID = Employees; EXEC SQL SELECT GivenName || ' ' || Surname, Sex, BirthDate INTO :name, :Sex, :birthdate:ind_birthdate FROM Employees WHERE EmployeeID = :ID; if( SQLCODE == SQLE_NOTFOUND ) { return( 0 ); /* Employees not found */ } else if( SQLCODE < 0 ) { return( -1 ); /* error */ } else { return( 1 ); /* found */ } } |
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