ABAP_to_the_Future

Database Access 2.1
efficient way to do this is by way of an inner join. However, it is somewhat
tedious to list all of the fields from the main table, as you can see in Listing 2.7.
SELECT zt_monsters~monster_name zt_monsters~monster_number
zt_monsters~sanity zt_monsters~strength
zt_monsters~hat_size zt_monsters~number_of_heads
zt_hats~bar_code
FROM zt_monsters
INNER JOIN zt_hats
ON zt_monsters~hat_size = zt_hats~hat_size
INTO CORRESPONDING FIELDS OF TABLE lt_monsters
WHERE monster_name = 'FRED'.
Listing 2.7 All Fields from Main Table
The preceding code reads everything from the monster table but just one minor
detail from the hat table. In 7.4, you can achieve th e same thing in a different
way, as shown in Listing 2.8.
SELECT zt_monsters~*
zt_hats~bar_code
FROM zt_monsters
INNER JOIN zt_hats
ON zt_monsters~hat_size = zt_hats~hat_size
WHERE monster_name = 'FRED'
INTO DATA(lt_monsters).
Listing 2.8 Reading Everything from One Table during an Inner Join
The key here is the asterisk. It acts just like the wild card in SELECT * and as such
can be abused if you really want not all the fields of the table, but just half of
them.
Warning: Houston, We Have a Problem
As always, using asterisks in such cases is the easy way out, but it slows down database
performance and—when you are creating the table at the same time—memory consumption
as well. This just proves that the more tools are at one’s disposal, the greater
the damage you can do with them if they are not used properly.
In addition to the asterisk functionality in ABAP 7.4, the syntax of inner joins has
also been extended so that now you have much more flexibility in defining the
relationship between the tables. An example of this is shown in Listing 2.9.
INNER JOIN zt_monster_pets
ON zt_monster_pets~owner EQ zt_monsters~monster_number
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