Fetch Statement
This statement retrieves a row from an open cursor and loads it into 4GL variables.
This statement has the following syntax:
fetch cursor_variable into variable_list;
You can use the fetch statement to:
• Move the cursor forward one row in the select statement's result table
• Put the values from the specified columns into the specified variables
• Set the State and RowCount attributes of the CursorObject class
After a successful fetch, you can process the values in the variables any way you want. To display the cursor data in the window, you can fetch it into the variables that are associated with the fields on your form.
The retrieved row becomes the current row, that is, the row affected by the next update cursor or delete cursor statement for this cursor.
You can use a simple list of variables whenever you:
• Retrieve all of the values in the result row, in the order specified by the select statement
• Retrieve a subset of the values that begins with the first value retrieved by the select and continues in the order listed in the select (stopping before all are retrieved)
You must specify the column names whenever you fetch the column values out of order, that is, not in the same order in which they were specified in the select statement. For example, if you select columns A, B, C, and D and then fetch columns B and D, you must specify the column names. When you specify the column names, you can fetch the columns in any order. If you retrieved values into resultnames in your select statement, use these resultnames as the columnnames in the variable list of your fetch statement.
The fetch statement can contain fewer variables than there are select expressions in the open statement, but it cannot contain more. Whether you specify the column names or not, the data types of the variables and the values that are assigned to them must be compatible. OpenROAD does not check the compatibility of the variables and column names until runtime. If there is a mismatch, OpenROAD reports it in the iierrornumber system variable, although the row is still fetched and becomes the current row.
If the fetch statement is successful, 4GL sets the value of the iirowcount system variable to one. If the fetch statement is unsuccessful or there are no more rows to fetch, 4GL sets iirowcount to zero and does not change the variables. Additionally, if a fetch statement finds no rows to fetch, it sets the State attribute to CS_NO_MORE_ROWS. Consequently, you can check the State attribute after each fetch to determine if there are more rows to fetch.
To find out how many rows have been successfully fetched, check the RowCount attribute of the CursorObject class. OpenROAD sets this attribute to zero whenever the cursor object is opened and increments it after each successful fetch.
You must issue any fetch statements for a cursor in the same DBMS session in which you opened the cursor.
For more information and examples of specifying columns in a fetch statement, and for a description of how to use cursors in OpenROAD, see the Programming Guide.
Parameters--Fetch Statement
This statement has the following parameters:
cursor_variable
Specifies a reference variable that points to an object of type CursorObject. This cursor must be open.
variable_list
Specifies the variables into which you load your data. You can format this list as:
:variable{, :variable}
or
:variable = columnname{, :variable = columnname}
You cannot mix the two formats.
Examples--Fetch Statement
Check the State attribute of the CursorObject to determine whether there are remaining rows:
fetch emp_cursor into :emp_name = name, :emp_age =
age;
if emp_cursor.State = CS_CURRENT then
/* A new row has been fetched. */
...
elseif emp_cursor.State = CS_NO_MORE_ROWS then
/* All rows have been fetched. */
...
else
/* There is an error. */
endif;
Check the RowCount attribute of the CursorObject to check the number of rows that have been retrieved:
/* Fetches no more than 5 rows from CursorObject */
if emp_cursor.RowCount <= 5 then
fetch emp_cursor into :emp_name = name, :emp_age =
age;
else
close emp_cursor;
endif;
Last modified date: 06/25/2024