DB2 programming skills (2)

1 DB2 Programming
1.1 do not use the TAB key after creating a stored procedure
Create procedure
You can only use spaces, but not tab keys, otherwise the compilation will fail.
Remember, remember.

1.2 use temporary tables

Note that temporary tables can only be created on user tempory tables space. If the database only has system tempory table space, temporary tables cannot be created.
In addition, the temporary tables of DB2 are not the same as those of sybase and oracle. The temporary tables of DB2 are valid in a session. Therefore, if the program has multiple threads, it is better not to use temporary tables, which is difficult to control.
It is best to add the with replace option when creating a temporary table so that the drop temporary table is not displayed, if you do not add this option when creating a temporary table and the temporary table has been created in this session and has not been dropped, an error occurs.
1.3 retrieve the specified first few records from the data table
Select * from tb_market_code fetch first 1 rows only

However, the following method is not allowed.
Select market_code into v_market_code
From tb_market_code fetch first 1 rows only;

Select the field of the first record to a variable in the following way
Declare v_market_code char (1 );
Declare cursor1 cursor for select market_code from tb_market_code
Fetch first 1 rows only for update;
Open cursor1;
Fetch cursor1 into v_market_code;
Close cursor1;

1.4 Use of cursors
Note: commit and rollback
When using a cursor, pay special attention that if the with hold option is not added, the cursor will be closed during Commit and Rollback. There are many things to note about Commit and Rollback. Be careful

Two Methods for defining a cursor
One is
Declare continue handler for not found
Begin
Set v_notfound = 1;
End;

Declare cursor1 cursor with hold for select market_code from tb_market_code for update;
Open cursor1;
Set v_notfound = 0;
Fetch cursor1 into v_market_code;
While v_notfound = 0 Do
-- Work
Set v_notfound = 0;
Fetch cursor1 into v_market_code;
End while;
Close cursor1;
This method is complex but flexible. In particular, you can use the with hold option. This method can only be used if the cursor is not closed due to a commit or rollback in a loop.