DB2 - cannot invalidate a view

Question

I work on something and I need to check some views. I use this code:

SELECT SUBSTR(T.TABNAME,1,32) AS TABLE, SUBSTR(T.TABSCHEMA,1,32) AS SCHEMA, T.STATUS, T.TYPE FROM SYSCAT.TABLES T WHERE T.TABNAME LIKE 'TEMP_T%'

To check if it works I:

• added a table,
• created a view of "SELECT * FROM TEMP_T",
• altered the table by adding a new column,
• and check the status again.

From what I understand (did a bit of research) this should invalidate the view, but it didn't. I also removed the initial column of the table (after creating the view), but the view still appears to be valid. In the end I even droped the table, but the view still is in STATUS='N'.

Can you guys help me understand why is this happening? I assume it's a bug in DB2, but as I'm new to DB I'd like to hear some other opinions.

Here is the log:

CREATE TABLE DB2INST1.TEMP_T ( COL_A  CHAR(5) )
DB20000I  The SQL command completed successfully.

CREATE VIEW DB2INST1.TEMP_V AS   SELECT * FROM DB2INST1.TEMP_T
DB20000I  The SQL command completed successfully.

SELECT SUBSTR(T.TABNAME,1,32) AS TABLE, SUBSTR(T.TABSCHEMA,1,32) AS SCHEMA, T.STATUS, T.TYPE FROM SYSCAT.TABLES T WHERE T.TABNAME LIKE 'TEMP_%'

TABLE                            SCHEMA                           STATUS TYPE
-------------------------------- -------------------------------- ------ ----
TEMP_T                           DB2INST1                         N      T
TEMP_V                           DB2INST1                         N      V

  2 record(s) selected.


ALTER TABLE DB2INST1.TEMP_T ADD   COLUMN COL_B VARCHAR(20)
DB20000I  The SQL command completed successfully.

ALTER TABLE DB2INST1.TEMP_T DROP  COLUMN COL_A
DB20000I  The SQL command completed successfully.

REORG TABLE DB2INST1.TEMP_T
DB20000I  The REORG command completed successfully.

SELECT SUBSTR(T.TABNAME,1,32) AS TABLE, SUBSTR(T.TABSCHEMA,1,32) AS SCHEMA, T.STATUS, T.TYPE FROM SYSCAT.TABLES T WHERE T.TABNAME LIKE 'TEMP_%'

TABLE                            SCHEMA                           STATUS TYPE
-------------------------------- -------------------------------- ------ ----
TEMP_T                           DB2INST1                         N      T
TEMP_V                           DB2INST1                         N      V

  2 record(s) selected.


DROP TABLE DB2INST1.TEMP_T
DB20000I  The SQL command completed successfully.

SELECT SUBSTR(T.TABNAME,1,32) AS TABLE, SUBSTR(T.TABSCHEMA,1,32) AS SCHEMA, T.STATUS, T.TYPE FROM SYSCAT.TABLES T WHERE T.TABNAME LIKE 'TEMP_%'

TABLE                            SCHEMA                           STATUS TYPE
-------------------------------- -------------------------------- ------ ----
TEMP_V                           DB2INST1                         N      V

  1 record(s) selected.

Answer 1

As for the view being valid after dropping a column: The view is defined as SELECT * so the view is still valid.

Regarding the validity of the view after dropping the table just use field VALID from SYSCAT.VIEWS, see below.

db2 => DROP TABLE DB2INST1.TEMP_T
DB20000I  The SQL command completed successfully.
db2 => SELECT SUBSTR(VIEWNAME,1,32) AS TABLE, VALID FROM SYSCAT.VIEWS WHERE VIEWNAME='TEMP_V'

TABLE                            VALID
-------------------------------- -----
TEMP_V                           N

  1 record(s) selected.

db2 => CREATE TABLE DB2INST1.TEMP_T ( COL_A  CHAR(5) )
DB20000I  The SQL command completed successfully.
db2 => SELECT SUBSTR(VIEWNAME,1,32) AS TABLE, VALID FROM SYSCAT.VIEWS WHERE VIEWNAME='TEMP_V'

TABLE                            VALID
-------------------------------- -----
TEMP_V                           N

  1 record(s) selected.

db2 => SELECT * FROM DB2INST1.TEMP_V

COL_A
-----

  0 record(s) selected.

db2 => SELECT SUBSTR(VIEWNAME,1,32) AS TABLE, VALID FROM SYSCAT.VIEWS WHERE VIEWNAME='TEMP_V'

TABLE                            VALID
-------------------------------- -----
TEMP_V                           Y

  1 record(s) selected.