Getting Started with DB2 Express-C

152 Getting Started with DB2 Express-C
ROWS clause because working in the DB2 Command Window will commit by default on
each statement entered.
8.3.6 Create Global Temporary Tables (CGTTs)
While DGTTs allow you to create a temporary table, the table definition cannot be shared
across different connections or sessions. Every time a session is established, the
DECLARE GLOBAL TEMPORARY TABLE statement has to be executed. With Create
Global Temporary Tables (CGTTs) on the other hand, the temporary table definition only
needs to be created once as it is permanently stored in the DB2 catalog. This means that
other connections can simply use the table without having to create it again. Though the
table structure can be used immediately, the data for each connection is independent from
each other, and will disappear after the connection closes. For an example, let's take a look
at Listing 8.9. It assumes a user temporary table space has already been created.
From DB2 Command Window #1:
db2 connect to sample
db2 create global temporary table mycgtt (col1 int, col2 varchar(10)) on
commit preserve rows
db2 insert into mycgtt values (1,'hello1'),(2,'hello2'), (3,'hello3')
db2 select * from mycgtt
COL1 COL2
----------- ----------
1 hello1
2 hello2
3 hello3
3 record(s) selected.
From DB2 Command Window #2:
db2 connect to sample
db2 select * from mycgtt
COL1 COL2
----------- ----------
0 record(s) selected.
Listing 8.9 - Working with CGTTs - scope
In Listing 8.9, we saw that within DB2 Command Window #2 (another session or
connection), there is no need to create the CGTT again, you can simply reference it;
however, no rows are returned because the data was particular to the first session.
8.4 Views
A view is a representation of the data in tables. The data for the view is not stored
separately, but is obtained when the view is invoked. Nested views, that is, a view created