Spec-Zone .ru
спецификации, руководства, описания, API
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Spec-Zone .ru
спецификации, руководства, описания, API
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ANALYSE([max_elements[,max_memory]])
ANALYSE() examines the result from a query and returns an analysis of the results
that suggests optimal data types for each column that may help reduce table sizes. 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;
if there are more than max_elements distinct values, then ENUM
is not a suggested type.
max_memory (default 8192) is the maximum
amount of memory that ANALYSE() should allocate per column while trying to
find all distinct values.