SQL/MP Reference Manual

HP NonStop SQL/MP Reference Manual—523352-013
C-81
CONTROL TABLE Directive
are not in the same order (such as in a repartitioning parallel plan), SQL returns an
error and does not choose the key-sequenced merge join method.
Because JOIN METHOD applies only to the inner table of a join operation, it is
ignored for a table that has a join sequence of 1. JOIN METHOD is normally used
only with the JOIN SEQUENCE option.
JOIN SEQUENCE { SYSTEM | sequence-number }
specifies the sequence in which SQL processes the table for the join.
JOIN SEQUENCE SYSTEM is the default; it directs SQL to determine the
sequence.
sequence-number is an integer that specifies the join sequence for the table
within a SELECT. For example, if you specify sequence-number as 3 for a table,
that table is third in the join sequence for a SELECT.
You do not need to specify sequence-number for each table in a SELECT; SQL
determines the join sequence for tables you do not mention in CONTROL TABLE
directives. For example, if you specify sequence-number as 3 for a table, but
have no CONTROL TABLE directives in effect for other tables, SQL determines the
tables that are first and second in the join order, in addition to those that are fourth,
fifth, and so forth.
sequence-number must be greater than zero and no greater than the number of
tables (or tables with different correlation names) participating in the SELECT. Two
tables (or two occurrences of the same table) cannot have the same join sequence
in a SELECT.
MDAM { OFF | ENABLE }
specifies whether to enable MDAM or turn it off.
You cannot specify MDAM OFF or MDAM ENABLE with the
CONTROL TABLE * command. The MDAM option must be associated with a
specific table.
When you specify MDAM OFF or MDAM ENABLE, SQL sets the ACCESS PATH
MDAM options to their default values, USE DEFAULT KEY COLUMNS and
ACCESS SYSTEM.
If you define a table with a clustering key and use a protection view, you will not be
able to use MDAM. For more information, see Protection View on page P-32.
OFF turns MDAM off for the specified table
ENABLE enables the use of MDAM for the specified table. This is the
default; ENABLE has an effect only if you previously specified
MDAM OFF or ACCESS PATH...MDAM ON for the table.