ArcGIS Server .NET Help - Example: Creating a database view in DB2 using the sdetable command

You can use the sdetable command to create a view in a geodatabase in IBM DB2. Doing so automatically registers the view with ArcSDE.

The example in this topic shows how a view created by sdetable can be used to restrict user access to specific data. The example is based on a table with the following definition:

CREATE TABLE employees(emp_id integer not null, name varchar(32), 
department smallint not null, hire_date date not null);

Notice that the table contains a not null integer column that can be used as an ArcSDE row ID.

Create a view using the sdetable command

Suppose you want the manager of department 101 to see all the columns in the table employees but only the rows for employees in department 101. Use sdetable to create a view with all rows in which the department number is 101. The –w option specifies the WHERE clause of the query stored with the view definition.

sdetable –o create_view –T view_dept_101 –t employees 
–c 'emp_id,name,department,hire_date' -w "department = 101" 
–u gdb –p gdb.bdg –i sde:db2 -s mydb2server -D testdb

Attribute        Administration Utility
__________________________________
Successfully created view view_dept_101.

For more information on the sdetable command, see the Administration Command Reference.

The sdetable command defines the view in the DB2 system catalog, just as if you created the view yourself using the DB2 CREATE VIEW command. To see this, query the DB2 SYSCAT.VIEWS system view.

db2 => SELECT viewschema, viewname, text 
FROM syscat.views 
WHERE viewname = 'VIEW_DEPT_101';

VIEWSCHEMA	VIEWNAME	TEXT
GDB	VIEW_DEPT_101	CREATE VIEW view_dept_101 AS SELECT = emp_id, name, department, hire_date FROM GDB.EMPLOYEES WHERE department = 101

VIEWSCHEMA

VIEWNAME

TEXT

GDB

VIEW_DEPT_101

CREATE VIEW view_dept_101 
AS SELECT = emp_id, name, department, hire_date 
FROM GDB.EMPLOYEES 
WHERE department = 101

View_dept_101 in SYSCAT.VIEW

ArcSDE adds the owner name to the table name in the query. If you create your own view with Structured Query Language (SQL), this is not done for you automatically unless you qualify the table name when creating the view.

Notice that the names of the view and its owner are converted to uppercase before being stored in SYSCAT.VIEWS. This is done by DB2, not ArcSDE. Therefore, when querying for these specific text values, you must type them in uppercase.

Caution:

Some users create registered views with sdetable –o create_view and alter the view definition using SQL. This is done to avoid complex sdetable –o create_view command line syntax (especially the –c option) or to include a more complex or extended view definition, such as one that uses connections to external databases. Although altering a view can solve some problems, it is also possible to create a view that does not work well with ArcSDE or ArcSDE clients such as ArcGIS Desktop.

Grant privileges on the view

The view owner can grant privileges on the view to specific users without having to grant those users access to the base table (employees). In this example, the user mgr100 is granted select privileges on the view, view_dept_101:

db2 => connect to testdb user gdb using gdb.dbg
   Database Connection Information
 Database server        = DB2 9.5.5
 SQL authorization ID   = GDB
 Local database alias   = TESTDB

db2 => GRANT SELECT ON view_dept_101 TO USER mgr100;
DB20000I  The SQL command completed successfully.

Note:

In this example, the table owner and the view owner are the same user. If they were different, the table owner would need to grant the view owner privileges to select from the table plus the ability to grant select to other users. If the privilege is granted using SQL, include the WITH GRANT OPTION in the statement. If the privilege is granted using the sdetable command with the grant operation, the inherit (–I) option must be specified.

Test privileges

db2 => connect to testdb user mgr100 using mgr100
   Database Connection Information
 Database server        = DB2 9.5.5
 SQL authorization ID   = MGR100
 Local database alias   = TESTDB

db2 => SELECT * FROM gdb.view_dept_101;

emp_id         name        dept      hire_date
29             YAN WU      101       04/15/2002
67             LEE VAN     101       11/01/2004
78             SUE CHOO    101       05/31/2005
105            DAN HO      101       10/01/2006
111            ANN ANG     101       12/15/2006
135            BILL BO     101       10/15/2007

As expected, only records for employees in department 101 are returned.

Views exist as schema objects, independent of the tables that populate them. In the following query, the user mgr100 has no access to the table, employees, so it appears to mgr100 that the employees table does not exist.

db2 => SELECT * FROM gdb.employees;
SQL0551N  "MGR100" does not have the privilege to perform operation "SELECT" 
on object "GDB.EMPLOYEES".  SQLSTATE=42501

11/18/2013