analyse([
max_elements
[,max_memory
]])
This procedure is defined in the
sql/sql_analyse.cc
file. It examines the
result from a query and returns an analysis of the results that
suggests optimal data types for each column. To obtain this
analysis, append PROCEDURE ANALYSE
to the end
of a SELECT
statement:
SELECT ... FROM ... WHERE ... PROCEDURE ANALYSE([max_elements
,[max_memory
]])
For example:
SELECT col1, col2 FROM table1 PROCEDURE ANALYSE(10, 2000);
The results show some statistics for the values returned by the
query, and propose an optimal data type for the columns. This
can be helpful for checking your existing tables, or after
importing new data. You may need to try different settings for
the arguments so that PROCEDURE ANALYSE()
does not suggest the ENUM
data type when it
is not appropriate.
The arguments are optional and are used as follows:
max_elements
(default 256) is the
maximum number of distinct values that
analyse
notices per column. This is used
by analyse
to check whether the optimal
data type should be of type ENUM
.
max_memory
(default 8192) is the
maximum amount of memory that analyse
should allocate per column while trying to find all distinct
values.