Oracle 5.0 Reference Manual page 497

Dynamic Variable
How the server treats
for tables. This variable has three possible values, nulls_equal, nulls_unequal, and
MyISAM
nulls_ignored. For nulls_equal, all
value group that has a size equal to the number of
are considered unequal, and each
values are ignored.
NULL
The method that is used for generating table statistics influences how the optimizer chooses indexes
for query execution, as described in
Any unique prefix of a valid value may be used to set the value of this variable.
This variable was added in MySQL 5.0.14. For older versions, the statistics collection method is
equivalent to nulls_equal.
• [477]
named_pipe
Variable Name
Variable Scope
Dynamic Variable
Platform Specific
(Windows only.) Indicates whether the server supports connections over named pipes.
•
net_buffer_length
Command-Line Format
Option-File Format
Option Sets Variable
Variable Name
Variable Scope
Dynamic Variable
Each client thread is associated with a connection buffer and result buffer. Both begin
with a size given by
Server System Variables
Yes
Permitted Values (>= 5.0)
Type
enumeration
Valid
nulls_equal
Values
nulls_unequal
nulls_ignored
values when collecting statistics about the distribution of index values
NULL
NULL
forms a distinct value group of size 1. For nulls_ignored,
NULL
Section 8.5.4,
named_pipe
Global
No
windows
Permitted Values
Type
boolean
(windows)
Default
OFF
[477]
--net_buffer_length=#
net_buffer_length
Yes,
net_buffer_length
net_buffer_length
Global, Session
Yes
Permitted Values
Type
numeric
Default
16384
Range
1024 .. 1048576
net_buffer_length
477
index values are considered equal and form a single
values. For nulls_unequal,
NULL
"MyISAM Index Statistics
[477]
[477] but are dynamically enlarged
values
NULL
Collection".